Hey there! As a beginner automation engineer, you're asking the right question. The technical specs are just the tip of the iceberg - the real hidden pitfalls come from the ecosystem around each platform. Here's what you need to watch out for:

1. Software Ecosystem Lock-in: Each PLC requires its own proprietary software - Siemens TIA Portal (€1,500-15,000), Rockwell Studio 5000, and Mitsubishi GX Works3 (€1,000-5,000). Once you invest in one, you're locked into that vendor's ecosystem for training, support, and future expansions.

2. Learning Curve Differences: GX Works3 takes 1-3 months to learn, while TIA Portal needs 3-6 months. Studio 5000 has its own steep learning curve. If your team already knows one system, switching costs can be massive.

3. Regional Support Networks: Allen-Bradley dominates North America with better local support, while Siemens has stronger global presence. Mitsubishi is popular in Asia. Consider where your maintenance team is located and what support they can access.

4. Third-Party Integration Headaches: Each system has different communication protocols and compatibility with third-party devices. Siemens tends to be more open, while Rockwell can be more proprietary. Check what other equipment you'll need to integrate.

5. Documentation & Community: Siemens and Rockwell have massive online communities and documentation. Mitsubishi has less English-language support. As a beginner, having access to tutorials and forums can make or break your project.

6. Hidden Costs: Beyond hardware, consider software licensing (subscription vs perpetual), training costs, and the price of hiring engineers familiar with each platform.

My advice? Look at what's already in your facility, consider your team's existing skills, and think about long-term maintenance. Sometimes the 'best' technical choice isn't the most practical one for your specific situation!