u should use all. u need to keep up ur skill on all three types, slash, crush, and pierce. there is nice stuff out there for each, plus some mobs are only hit by one kind.
if ur asking about which type in slashing, each type with have a different delay and damage, but they are usually combined into a damage rating, sorta easy way to tell how much it deals(all things being equal). there are plenty of reasons for qwick weapons, as well as long delay weapons. it all depends on the stradegy. mess around with how u play and different types, see what works, but theres no harm in having more than one weapon.
i personally got lucky and found a 1h pierce <posion laced spear> on broker(selling for less than the vendor price). great stats and a 44.1 rating, which is better than my 2h axe ;o/ i cant find it on any sites, so no idea where it came from.