Bearings are one part of a rolling system. Wheel diameter, contact patch, truck alignment, spacers, speed rings and axle tension all affect how a setup feels.
Check the whole wheel
If a wheel feels slow, first check that it is not rubbing the truck, that the bearings are seated and that the axle nut is not over-tightened.
Make one change at a time
Adjust one part of the setup, test it, and keep notes if you are troubleshooting. That makes the real cause easier to find.