[DonRotolo]

I'd fall back on Scouting. Pretend you're scouting the robot during competition, and make a list of all its actual (not claimed) capabilities in the game for which it was designed. Just be more detailed than usual. Just be realistic: No sense in rating the ramp ability of an Overdrive robot, that wasn't a design goal.

Then pick a few common characteristics (Speed, agility, robustness, climbing ability, etc.) and compare them using the same criteria. These measures may help discern the "Best Drivetrain" or somesuch.

Spend an hour or 2 with each robot, have several students do the rating of the same categories, and have fun.