Stephen, thanks for the question. The B version is the one we're racing - It has a Slot.it Flat6 motor, as compared to the MR1041 which has the full height long can motor. The difference will be in the motor pod and the motor itself, and how the motor applies power. The "bigger" can motors tend to have more torque where the lower profile Flat 6 motors have a lower CG. Does that answer your question?