I was talking about an octagon base with a wheel on each face, so 8 driven wheels.
if you only look at speed/torque and you discount the extra 4 wheels of weight; Going forward, an x drive with 2 motors per wheel has 8 motors at sqrt(2)/2 of their regular power which equals ~5.66. An octodrive has 2 motors at full power and 4 motors at sqrt(2)/2 power which equals ~4.83. Going backwards and strafing is the same numbers and diagonal for an X drive is 4 motors at full efficiency and for an octodrive, ~4.83.
Conclusion: x drive is better at forwards/backwards/strafing but octodrive is better at diagonals. Given the extra weight of an octodrive, the complexity and potential interference with the feeder mechanism and most drivers rely more on forwards/backwards/strafing than diagonals, I would prefer an x drive. My math might be wrong.