[lukevanoort]

The best drive train is one that gets your robot (and other robots your robot might be "kindly escorting", depending on your strategy) from point A to point B as quickly and reliably as possible. Since 2005, the most successful drive train has been the 6WD (based off of the composition of the championship finals alliances, where 61% of teams since 2005 have used one), usually with a lowered centre wheel. However, as Eric said, driver skill and practice are the single biggest determinant in how well a robot performs (well, next to being turned on, but I don't think that really counts). Build it simple, build it sturdy, build it with enough speed, build it maneuverable, build it with a decent amount of traction, and most importantly, build it early so the drivers can practice. If you do all of those, you'll have a very effective drive system.