even with an optimized set as fury the most crit you are going to get is like 13k
though fury probably does better ST if you have enough luck and cleave and is now a little less dependent on BT crits with Stormbolt doing pretty nice damage
but i prefer arms all day every day. fury just doesn't have a lot going for it, for me it was even just impossible to get gold in PG because of the complete lack of consistent damage. didnt crit, couldnt rb, was always out of rage. very unreliable. cakewalk as arms.
I should really try to redo some Challenge Modes as a dps.
Back in 5.0/5.1 I did them in Fury spec and it was decent. Now, with the Bladestorm buff and the RB buff, I expect the Fury spec t be totally viable in there.
And yes, Arms spec is supposed to be better than Fury spec in CMs, especially in 5.4. So I expect the spec to be REALLY good now.
Arms is way to go, fury lacks fluent rotation which can cause lack of damage to trash and bosses. Fury has great single/multi target burst with cd's up as arms requires no crits, they are just a bonus. Arms also has strong Deep Wounds, all around cleave (tho t16 2pc does not work there, so you might find yourself rage starved sometimes) and it's single target is better at the 463 ilvl range.
But if you are not aiming for realm best times/world best times if you can go which spec you ever prefer.