...I may be way off base here..and If I am I'm sure someone will correct me...
But I think of the rotor this way, in comparison to a BRUSHED/WOUND armature.
Small Arm/ few turns...HI RPM/
Big ARm/lots of turns ie: STOCK...LOW RPM
More turns yet - LOWER RPM (like the motors used on some dynos that had like 50 turns)
...similarly - a small diam. 'sintered' rotor, should be HIGHER RPM where something like the newer 'tuning' sintered rotor Novak makes, would create a lower rpm.
The lower rpm motors I believe will produce more torque.
between the sintered and bonded rotor...the bonded rotor is large in diameter and has very little magnetic strength compared to a sintered rotor. (You can tell this as easy as trying to pull a sintered rotor from the motor..it almost takes FORCE and the use of PLIERS, where a bonded rotor has so little magnetic pull..you can't hardly feel the resistance when removing it from the can.
More magnetic force - should produce MORE pull/power.
....does that make sense...or am I off someplace?