Well, once an electroplated wheel is worn out, it's finished.
A resin-bound wheel, on the other hand, can be redressed quite easily. I personally use a white aluminum oxide stone (these are marketed as dressing stones by Norton Abrasives and Tyrolit Grinding). You manually feed the stone into the wheel until it's cleaned up. After this treatment, the wheel cuts as it should. I've observed that many people using abrasive grinding wheels find them clogged with soft steels and other materials, such as the residue from marking with Sharpies, which severely clogs the wheel.
I personally prefer resin-bound wheels, but the choice also depends on whether it's for roughing or fine grinding. The wheel mentioned earlier is still a very coarse one.
