I have personally dealt with open diff's and locking diff's in my vehicle. My truck had the stock rearend with the open gears in it, it behaved by doing great in traffic but off-road it sucked if you got one rear wheel in dirt/gravel/air that wheel would spin and the vehicle would go backwards (I forgot to mention I have a 2wd). So I bought a powertrack locking diff and it kicks butt because it "ratchets" around corners using plates to unlock the rear wheels together however it is temperamental and you can’t WOT around a corner or else it will lock up. I can go into a corner and floor it (WOT) the locking diff will lock causing the wheels to chirp and the truck's turning is greatly decreased. When it receives alot of torque from the motor and one wheel slips it will engage and lock the two rear wheels together this makes it great offroad and when doing burnouts (no more pegged leg burnouts ;P).
I doubt that there would be a situation in this years game where you’re robot would have ½ of the drive wheels on one side of the roboto off the ground and thus, an open diff would be a good mechanical means of keeping the wheels nice and smooth through turns.
And here’s a great article on how open diff’s work
http://auto.howstuffworks.com/differential2.htm
I like the idea of programming a “diff” though.