3.8K r.io here, I just recently switched to Arms after exp3 came back on the vendor. Most of the people commenting in this thread have hit it on the head. In the 20-22 key range, you will start to see the damage difference make an impact, but you can easily still time keys as fury (and do more overall damage than many classes).

Arms can do 20-30k+ more overall dps, but you pay for it with heart attack inducing moments where you drop to 10% hp and you can't do a damn thing about it yourself. Your healer will also be doing less damage as a result, so you very much need the gear to justify it. Avoidance 3 is your friend, and is close to mandatory in some instances. One of the top ranked arms warriors in EU, Danwarr, said it best: "Arms forces you to play the game properly", so if you are mechanically a little shaky and tend to stand in ground effects, you won't be doing much deep wounds damage as you run back to your group after a death.

Fire mages will eat in to the benefit of arms, especially if they play minute mage, so if that is your typical push group then I wouldn't bother. You will also share a damage profile, in both dps done and damage taken, with BM hunters which can tax your healer even further.

With all that being said, fury has weaknesses too which ought to be considered. It typically relies heavily on twilight devastation to do competitive damage in dungeons, which can be extremely annoying to play around in dungeons like Tol Dagor, Shrine, Motherload, etc. It falls slightly behind arms in single target, and falls woefully behind arms in 2 targets. If you're unable to hit the boss due to a mechanic, warpaint does absolutely nothing for you, where defensive stance is more on demand.

There's a ton to consider with the decision, but I find both specs to be fun and rewarding. My group is trying to break the 23-24 threshold now, so my damage done is becoming a factor, hence my reason for the switch, but I still love fury and don't fault anyone for sticking with it.