[Deep Dark]

Someone may have already posted something similar, but I personally like direct driving at least one wheel per drive side. That way, if the chain does come loose during a match, you aren't limping around on the field driving in circles. In this year's game, if this occurs near the lap readers, you can get docked points for driving in circles, depending on robot position.

My personal favorite design features a 6 wheel drive, with the center wheel directly driven with two sprockets, each going to their own respective outer drive wheels. That way, the whole robot consists of 4 chain loops, and even if all of the chain breaks or falls off the sprockets, you can still drive fine.

And a switching gear transmission helps with varying speeds, since many, like the AndyMark Supershifter, can have alternative gears that can be switched out to achieve different drive ratios. In many cases, this becomes faster than having to change sprockets on all 4 or 6 wheels, since you 'simply' need to remove, disassemble, and reassemble both drive transmissions.

Anyway, that's my $0.02