Originally Posted by JoeG
The math checks out. An N-motor, Y-ratio "X" drive will move faster than an N-motor, Y-ratio tank drive. However, this is a little bit misleading. For a single speed system, you loose signifigant amounts of torque in the "X" drive. Therefore, the N-motor tank drive can be safely geared faster than the N-motor "X" drive, cancelling out the difference if we're talking about two separate robots.
Of course we're not saying you can just get magic speed out of nowhere! You can drive in x when you need speed or strafe (and torque doesn't matter as much), and then switch to tank when you need torque closer to the end of the match where you might need to push against another robot.