As above...

I sharpen ALOT of different kinds of knives, kitchen knives mostly. Different blade styles seem to do better on different size stones as well. The general grit and cutting power mentioned above is what is needed to make the bevels in the first place, but shape of stone as well as manufacture of stone can make a difference. Some stones do well with stainless or carbon steels, while not being that good with the other steel.

Does it make a difference to someone just starting out or not a heavy user? Not really they can get by with just about any stone and make due.

Plus I NEEEED em