Arms is meant to be for PvP use mostly because of the burst damage, that burst damage would cause too much aggro, as for Fury, it is meant mostly for PvE because although u hit less harder than a Arms warrior, u do around the same damage over the same time period because u attack alot quicker especially with flurry procs. That damage gets somewhat spread out similar to DoTs. But Fury can make a viable PvP spec if used correctly. A 31/30 MS Dual Wielding spec is actually quite effective, especially against casters (Prisets, Locks) because of Death Wish which will make u immune to fear for 30 secs. Since ud be dual wielding ud interrupt their casting alot similar to a rogues ability to do so. Plus the MS debuff reduces Healing by 50%. Bloodthirst is not meant for PvP.

So in conclusion, MS build whether 2 handed or dual wielding ( if used correctly), Bloodthirst for PvE only.