Wheel spacers will increase the scrub radius and position the wheels farther out. One of the effects of this is that, in a turn, the outer part of the tire will be farther forward or rearward and closer to the inner fender. A three-inch lift may raise the inner fender above the wheel center line and minimize the potential for rubbing, but an increased tire diameter will raise the center line of the wheel by half of the diameter increase.
Also, increasing the wheel diameter will change the effective final drive ratio. This will not only affect the speedometer and increase wear due to stress, but reduce acceleration and lower the RPM at a given speeds, and below the power band at cruising speeds. The result is more accelerating to and excessive downshifting to maintain speed on inclines. The remedy for this is to re-gear the differential(s) to compensate.
If wheel spacers damage wheel bearings, they will damage old and new.