You have asked 3 separate questions:
Define best. If by best you mean "have the highest intensity of properties" then the answer is: It's a tie between val hammers, val runic chisels, barbed sewing kits, and frostwood saws/feltching kits, but yes. If by best you mean "most useful", then the answer is theoretically yes, because of the previous answer being yes, but in practical cases, no.
Yes, other hammers have plenty of purposes. There are some reforges that are simply not possible (or are vanishingly rare) with a val hammer, but are with others hammers, quite common.
No, smithing hammers make terrible PvP weapons. That is technically what you asked, if you read the question literally.
What I think you were trying to ask is: Do any weapons made with valorite hammers make good PvP weps? The answer here is probably yes, but I've never seen/heard of anyone doing it. Most people like 20% splintering on a PvP weapon, but splintering is not reforgeable.
The nature of the mechanics of reforging mean that, especially for smithing, valorite hammers are hard to use effectively. They're simply too un-predictable to use easily.
