AC motors are really great if you're building a drivetrain from scratch. You get a cheaper gearbox (single speed, no reverse) and a cheaper motor (theoretically) by paying for roughly six times the electronics (although you can divide the current capability of everything by the square root of three). And it drives just like an automatic transmission, only better.<p>But with a conversion vehicle the gearbox comes for free with the donor car, and it's typically <i>more</i> work to integrate a single-speed drive than to just adapt the motor housing and shaft to the transmission bellhousing and flywheel. And you're not paying the early adopter tax that's still present on AC drivetrains.