What makes a motor hard to spin?

[zeropointbug]

Yes, precisely.

Also, the difference between the cores of slotted and slott-less motors are:

Slotted: Has coils wound in and around iron 'slots' that run length wise the motor, which creates the defined notch when you turn the shaft.

Slot-less: Has the coils wound in and around themselves, and compared to a slotted design, I believe they use more copper. There is only an iron 'blanket' around the coil to help intensify the field when running, and to shield components around the motor from intense AC magnetic fields.

[kazuaki]

So is the feel any indication of the power of the motor?

[aqwut]

Originally Posted by kazuaki

So is the feel any indication of the power of the motor?

no, I wouldn't think so...

[zeropointbug]

LOL Nope, no sir. It has nothing to do with how much power it's capable of, however, a larger motor will obviously have more 'resistance' than a smaller motor, so in that respect yes; but the power is limited by the stator really, you can only get so much power out of a given amount of copper material, at least according to the design theory of a DC brushless motor.