Dont know about SPv3, but SPv2 is 95% identical to Duo1 motors. The rotor, sensor, design are the same. Maybe the copper wires inside the can are different.
In terms of performance, SPv2 and Duo1 are about equal. Both are very good motors.
SPv3 claims to be 20% more efficient than SPv2 (on SP website). I like the 'plug in' style for ABC phase wires. It make swapping motors easier.