[John]

Additionally, the acceleration of the robot will be cut approximately in half. This may or may not be a big deal depending on the game and what you are trying to do, but it could potentially make the difference between getting away from a defensive robot and them staying in front of you.

For 2009, many teams went with two motors because the low friction meant that any additional torque beyond what two CIMs provide would likely be wasted. Also, if you have a lighter robot the drop in acceleration may be less noticeable.

The obvious advantage to using only two CIMs in drive is allowing them to be used elsewhere. However, this past year the large number of other relatively high power motors (FP, 4 Banebots) made this much less important.