-Best sometimes means cheapest.
ac is not the cheapest
-best sometimes means most bang for the buck
some argue that it does, but for the cost/hp, series seems better right now)
-best sometiems means most efficient
ac is more efficient, has regen capability and to control RPM you control the frequency, and to control torque you control the current.
-the best sometimes means simplest
DC is more simple, less wiring, less parts on the controller, less programming
-the best sometimes means less maintenance
DC has the maintenance of brushes, bearings and comms. AC only has the bearings.
so, see if that helps you decide. You can get the motor and controller for a 144V car for under 1500 for a motor, and under 2000 for a controller. You just can’t get AC for that, not yet, and not with any useable power for a car.