How important is it for bearings to be easily turned?

This is on a new MXUS turbo motor. One side the bearing is really smooth, with the cover off and spinning it on my finger it will spin for over 10 seconds by itself.

The other side is more stiff, harder to turn, and will only spin for a second on my finger then stop. You can feel it is harder to turn, but it is still easy to turn it on my finger. I feel no grind in the bearing also, just feels a bit stiff.

But at the end of the day, this little resistance is nothing with a big heavy hubmotor, so how much does it really matter? Perhaps, it is normal for bearings to be a little stiff?

It should be packed with grease and have rubber seals, so it will be a bit stiff. Honestly, I'd be more worried about the one that spins for 10 seconds. If it's properly greased, that shouldn't happen. Might want to think about replacing them both with some quality Japanese bearings. It may save you a problem later on.

If one bearing is stiffer to turn than the other, the stiff bearing will run hotter. How hot? only you will ever find out if...maybe it runs barely warm, or...hot enough that it damages the rubber side seals, leading to an early death.

You might be fine, who knows?

The only thing to worry about is the bearings being greased and sealed. The seals are held down by a nut or cap, which can be loosened or tightened - too loose and its not sealed, so will leak grease - too tight and the bearings won't slip. There is a "just right".

If you don't feel some click click click on your finger, the bearing is fine. Stiff from the seals is normal. The other one might be leaking.

I would not replace either one, unless it clicks or exhibits side play.