Pro-FRC: FRC's greater selection of acceptable materials and larger size has a greater potential for learning, and the sheer size of the robot and complexity of the games allow for more students to actively participate in robot design and implementation.
Pro-VRC: VEX's smaller size and limited materials has its potential in a wholly different area--flexibility of design. To design around these limitations is also a challenge worthy of student attention. And VRC games are arguably as complex as FRC games.
Pro-FRC: True, but VEX parts tend to oversimplify "real-world" possibilities with standardized parts, hence does not fully engage that entire design process (i.e. we don't often use CAD for VRC)
Pro-VRC: But the length of a VRC season allows for continual improvement and consequently concept development, which, contrary to short seasons of frantic building, is also more realistic.
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I find the learning opportunities provided by the two competitions to compliment each other very well... we've had teams in FRC for 7 years and VRC/FVC for four or five.
It certainly helps that students in VRC get more "hands on" time and have the chance to rebuild several times over the course of the season. This definitely reduces the pressure... but on the other hand, FRC cranks up the intensity and pressure and that's good, too.
FRC, with the larger teams and bigger budgets also brings unique opportunities... for instance, I've never heard of a VRC team with an entire PR or business team dedicated to "hands off the robot" functions... but FRC certainly branches far away from purely building, programming and driving a robot in terms of the skill set needed for a team to be successful.
