[MrJohnston]

What others have stated here is dead-on.

Every off-season, our club builds two or three bases with different drive systems so that even newer students to the club have a background in building them and so that we keep our skills with different drive trains strong.

Then, as a part of our design process, we choose a drive train from those we know how to build. (No experiments with drive trains during build season! We want to maximize the time we have to spend on the manipulators.)