[EricH]

Y'all forgot the biggest reason not to go with Ackerman drive. It's called Swerve Drive. For making two more wheels able to turn (and the two that turn in Ackerman turn more fully), you get to move in any horizontal direction without turning at all!

Besides the limited turning ability--an Ackerman has to do a Y-turn to accomplish what a skid can do with a simple spin--it's a somewhat complex drive. While swerve (or mecanum or omni) is also complex, it's somewhat of a simpler type of complex.