I spent two year at UP in their bridge design group. I took the Civil/Structural PE but most of the engineers elected to take the Civil/Transportation. I came from a structural background, so there was never any doubt about which exam I wanted to take. However, it seemed like most of the engineers at the UP opted to take the Transportation PM. I understood that most of them felt the Transpo PM was easier than the Structural PM - at least, based on their background.
Honestly, the PE doesn't mean much at UP. Nearly 100% of the design work is contracted to consultants, so the engineering roles are primarily project management roles. If your on the consulting side, the PE is probably more meaningful and likely to be used. Your role in the consulting organization and your career plans should inform you as to which exam to take. i.e. - if you want to be in structures design, take the structural, if you want to be in track design, take the transportation. There are also geographic considerations - I ended up sitting for the Illinois SE because of their title act and the fact that UP has track throughout IL. If you're doing work for a railroad that operates in states where the difference between a Civil/Structural PE and a Civil/Transportation PE is meaningful, investigate the differences to inform your decision. To be honest, I'm not sure that distinction exists in any state, but it's something to consider.
Finally, if you just need the title to qualify for a raise or promotion and it's clear that you won't be using the PE, the safe play is probably to evaluate which exam you are more comfortable taking and go that route. Let me know if you have any other questions - either here or through PM.
