Speaking from direct experience here. There are some big differences between the VEX and FTC programs both technical and event related. My teams are in New Zealand where VEX out numbers FTC 10:1 but just using momentum alone to decide on which program to implement isn't wise and I'll explain a few differences to highlight why.
VEX -12 month season with fairly simplistic game albeit very strategic once you hit worlds. We always see design convergence and even direct copying, perhaps driven by parts constraints and optimal solution development prior to worlds. Limited to small motors with over current tripping being enemy #1. A more level playing field due to VEX EDR constraints although this isn't a bad thing. Unique innovations are hard to achieve but teams rise to the challenge each season. Cost wise VEX can be surprisingly expensive for a competitive team.
FTC - 8 month season and more complex game. Some design concept convergence but nearly every robot looks unique. Almost completely open mechanical parts so use any robotics set you like including VEX parts with the flexibility to 3D print and manufacture your own special parts as required. COTS bearings and other assemblies are also permitted. High power motors and servos mean you have greater scope to create what you want. Truly innovative solutions can be developed simply because materials aren't constrained. Initial cost outlay is very much on par with VEX EDR.
More events is a double edged sword and we often see VEX teams that just aren't ready on the day due to inadequate preparation time with perhaps a slightly casual "oh well there's always next time" attitude. With less events FTC teams seem more prepared since each one is important.
Another fundamental differentiator is the VEX driver and programming skills challenges. These allow a team to show off what they're capable of alone and often find this rewarding because the benchmarks are their own without reliance on an alliance partner.
Don't worry this isn't an FTC sales pitch. We do FTC and VEX programs because they both have merit and outcomes we're looking for. Being able to utilize a school machine shop or the design department's laser cutter and 3D printer for making custom robot parts really steps it up a notch for schools. This coming season FTC teams are moving to Android devices for control which is opening up possibilities for attracting a wider spectrum of participants. Want to write phone apps? Cool. Want to write phone apps to control robots? Cooler
