[joshsmithers]

This is a tough trade-off situation, and I can honestly say I would never come to a definite conclusion on this. After pondering 269s sworm drive and Andy B's post, I would suggest a more traditional swerve. Like Al said, the drivetrain, where you should be maximizing your efficiency, just isn't the right place for worms. Also, worm gearing needs to be aligned to perform at its best. However, it may save a pound or two if you aren't using a bunch of spur gears. I have no idea what swerves typically weigh, but it's always a good idea to design with weight in mind.

I have no experience with swerves, but I would asume that if you don't want your wheels to backdrive when being pushed, then you could just turn them perpendicular to the pushing force.