PLC Platform Comparison
Comparing Siemens, Allen-Bradley, Mitsubishi, Omron and Schneider PLC Systems
Choosing a PLC platform is a long-term engineering decision.
The controller itself is only one part of the consideration. Programming software, existing engineering knowledge, communications, HMI and SCADA integration, spare parts, lifecycle support and the automation already installed across the facility can all influence which platform is appropriate.
Siemens, Allen-Bradley, Mitsubishi Electric, Omron and Schneider Electric all provide established industrial automation platforms, but they have different ecosystems, engineering environments and installed bases.
There is therefore no single "best PLC" for every application.
This guide compares the major PLC platforms Stratos encounters within industrial automation environments and highlights the factors manufacturers should consider when selecting a platform for a new project, standardising a facility or modernising an existing control system.
Siemens PLCs
Siemens has a significant installed base across industrial automation, particularly within European manufacturing environments.
Current Siemens automation environments commonly centre around the SIMATIC S7 family, with platforms such as S7-1200 and S7-1500 used across machine and process applications.
Engineering is increasingly centred around the TIA Portal environment, bringing PLC programming and other Siemens automation components into a common engineering platform.
Siemens PLCs may be appropriate where:
Siemens automation is already installed.
PROFINET is widely used.
Integration with Siemens HMI or SCADA is required.
A standard platform is needed across machines or production areas.
The organisation already has Siemens engineering capability.
Older Siemens environments may still contain S7-300, S7-400 or other legacy systems, making lifecycle and migration planning an important consideration.
Allen-Bradley PLCs
Allen-Bradley, part of Rockwell Automation, has a substantial industrial installed base, particularly in North America but also across multinational manufacturing operations.
Modern environments commonly use platforms such as CompactLogix and ControlLogix, with programming and configuration typically carried out through the Rockwell Automation engineering ecosystem.
Allen-Bradley may be appropriate where:
Rockwell Automation is already the site standard.
ControlLogix or CompactLogix systems are already installed.
EtherNet/IP forms a major part of the control network.
Machinery is supplied around the Rockwell ecosystem.
Internal engineering teams already support Allen-Bradley.
For UK manufacturers operating equipment originally designed for North American markets, Allen-Bradley PLCs are also commonly encountered within imported production machinery.
Mitsubishi PLCs
Mitsubishi Electric PLCs are widely used within machine automation and manufacturing equipment.
Their PLC ranges have historically included the FX and Q Series, with newer automation increasingly moving towards platforms such as the MELSEC iQ-F and iQ-R families.
Mitsubishi can be particularly relevant where:
Mitsubishi automation is already installed.
The application involves machine control.
Existing production machinery uses Mitsubishi PLCs.
Mitsubishi drives and other automation components are present.
Standardisation around the Mitsubishi ecosystem is desirable.
As with other manufacturers, facilities containing older Mitsubishi PLC generations should consider hardware availability, software compatibility and future migration requirements as part of lifecycle planning.
Omron PLCs
Omron has a strong presence in machine automation and manufacturing environments, with PLC and machine control technologies used across a variety of OEM and production applications.
Depending on the generation of equipment, sites may encounter established PLC families alongside newer NJ and NX automation platforms.
Omron may be appropriate where:
Omron automation is already established within the facility.
The application is machine-focused.
Existing OEM machinery uses Omron controllers.
Motion, I/O and machine automation need to operate within the same wider ecosystem.
Engineering teams already have Omron experience.
When assessing older Omron-controlled machinery, the PLC should be considered alongside the HMI, communications and other automation components forming part of the machine.
Schneider Electric PLCs
Schneider Electric provides PLC and automation technology used across industrial, process and infrastructure environments.
Depending on the age and application, facilities may encounter several generations of Schneider or Modicon controllers, with modern environments including Modicon M241, M251, M262 and M580 families.
Schneider may be relevant where:
Modicon systems are already installed.
Schneider automation forms part of the facility standard.
The control system needs to integrate with other Schneider technologies.
Existing infrastructure or process equipment uses Schneider controllers.
The organisation already has engineering capability around the platform.
As with other long-established PLC manufacturers, migration planning can become important where older controller generations remain operational.
Comparing PLC Programming Environments
The engineering software used to develop and maintain the PLC can be just as important as the controller itself.
Different platforms have their own engineering ecosystems.
For example, modern Siemens environments are commonly associated with TIA Portal, while Rockwell Automation uses its own Studio engineering environment. Mitsubishi, Omron and Schneider similarly provide manufacturer-specific programming and configuration software.
When comparing platforms, manufacturers should consider:
Software licensing.
Engineering workstation requirements.
Software version compatibility.
Internal engineering experience.
Availability of external support.
Backup management.
Online diagnostics.
Existing software standards.
Introducing another PLC manufacturer into a facility can therefore create additional requirements beyond simply stocking another controller.
PLC Communications and Industrial Networks
The PLC needs to communicate with the wider automation environment.
Depending on the platform and application, this may involve technologies such as:
PROFINET.
PROFIBUS.
EtherNet/IP.
Modbus TCP.
Modbus RTU.
Industrial Ethernet.
OPC UA.
Manufacturer-specific protocols.
Siemens environments frequently make extensive use of PROFINET, while EtherNet/IP is strongly associated with the Rockwell Automation ecosystem.
However, modern automation platforms increasingly provide ways of communicating beyond their native ecosystem.
The important question is therefore not simply which protocols a PLC supports, but how easily it can integrate with the equipment already installed within the facility.
HMI and SCADA Integration
PLC selection should also consider the supervisory and operator systems surrounding it.
A PLC may need to communicate with:
Local HMIs.
SCADA systems.
Historian systems.
Industrial dashboards.
Remote monitoring.
Reporting systems.
Other PLCs.
Higher-level production systems.
Using components from the same automation ecosystem can sometimes simplify engineering and diagnostics.
However, many industrial facilities operate mixed environments where PLCs from several manufacturers communicate with a common SCADA platform.
The appropriate architecture depends on the existing systems, future requirements and how much standardisation the organisation wants to achieve.
PLC Lifecycle and Obsolescence
PLC selection should not be based solely on current functionality.
Industrial control systems can remain operational for 15, 20 or even more years, meaning lifecycle support becomes an important consideration.
Manufacturers should consider:
Product lifecycle.
Hardware availability.
Spare parts.
Software support.
Operating system compatibility.
Migration paths.
Engineering knowledge.
Availability of replacement components.
Older PLCs can remain extremely reliable, but the operational risk increases when replacement hardware and engineering tools become difficult to obtain.
A good PLC strategy therefore considers how the platform will be maintained and eventually modernised.
Standardising PLC Platforms
Facilities that have developed over many years often contain several PLC manufacturers.
This can happen because machinery is purchased from different OEMs, projects are delivered by different integrators or technology standards change over time.
A mixed PLC environment can increase requirements for:
Engineering software.
Software licences.
Spare parts.
Engineer training.
Programming knowledge.
Backup management.
Network support.
External specialist support.
Standardisation can reduce some of this complexity.
However, that does not mean replacing functioning PLCs purely to achieve one manufacturer across the facility.
A more practical approach may be to establish a preferred platform for future projects while gradually addressing older systems as they reach an appropriate point for modernisation.
Which PLC Platform Should You Choose?
There is no universal answer.
For many industrial facilities, the most appropriate PLC platform is heavily influenced by the automation already installed.
Before selecting a platform, consider:
Existing installed base: If most of the facility already uses one manufacturer, introducing another platform needs a clear justification.
Internal skills: Consider which platforms maintenance and engineering teams can support.
OEM requirements: Machinery suppliers may have established control standards.
Industrial networking: Consider compatibility with existing networks and equipment.
SCADA and HMI: Determine how the controller will integrate with supervisory systems.
Lifecycle: Consider long-term hardware and software support.
Standardisation: Determine whether the project supports or complicates the wider automation strategy.
Support: Consider whether appropriate engineering expertise is readily available.
For a new greenfield system, the decision may be relatively open. For an existing manufacturing facility, the surrounding automation environment will often have a much greater influence.
Why Stratos Works Across Multiple PLC Platforms
Industrial facilities rarely operate a perfectly standardised automation environment.
A single factory may contain Siemens PLCs controlling one production area, Allen-Bradley controllers within imported machinery, Mitsubishi PLCs in another machine and older systems that have remained operational for decades.
Stratos works across multiple industrial automation platforms, including Siemens, Allen-Bradley, Mitsubishi, Omron and Schneider, allowing our engineers to consider the wider automation environment rather than automatically recommending a particular manufacturer.
This is particularly important for PLC modernisation and automation strategy projects, where the correct decision may be to retain one system, migrate another and establish a preferred platform for future investment.
Choosing the Right PLC Platform
PLC selection should support the wider automation environment, not create unnecessary complexity within it.
Whether you're choosing a PLC for a new automation project, dealing with several manufacturers across an existing facility or deciding how to replace obsolete controllers, Stratos can assess the technical and lifecycle implications of the available options.
Speak to our engineers about PLC platform selection, PLC programming, integration or PLC modernisation.
Frequently Asked Questions
Which PLC manufacturer is best?
There is no single best PLC manufacturer for every application. Siemens, Allen-Bradley, Mitsubishi, Omron and Schneider all provide established automation platforms. The appropriate choice depends on the application, installed equipment, engineering capability, industrial networks and long-term automation strategy.
Is Siemens better than Allen-Bradley?
Neither platform is universally better. Siemens has a particularly strong European installed base and is closely associated with PROFINET and the SIMATIC ecosystem, while Allen-Bradley has a major North American presence and is strongly associated with the Rockwell Automation ecosystem and EtherNet/IP. Existing site standards often influence the decision significantly.
Should a factory use one PLC manufacturer?
Standardisation can reduce software, spare parts, training and support requirements, but replacing reliable equipment solely to achieve standardisation may not be commercially justified. A preferred platform can instead be established for future projects and planned modernisation.
Can PLCs from different manufacturers communicate?
Yes, in many cases. Modern PLCs can communicate using industrial protocols and interfaces such as PROFINET, EtherNet/IP, Modbus and OPC UA, although compatibility and architecture should be assessed for the specific equipment involved.
When should an older PLC be replaced?
Age alone does not necessarily justify replacement. Consider manufacturer support, spare parts availability, software compatibility, reliability, production criticality and the consequences of failure. Where the operational risk becomes unacceptable, a planned PLC migration may be preferable to waiting for a failure.