It really depends on what you want to do, but at least for low level (~40+) dungeons, you won’t have any issues tanking as Arms or Fury, with Arms offering some nice talents for tanking, like Tactical Mastery. Personally, I went Arms. Here’s a little low level Warrior tanking guide I put together, and would love some feedback on.
Solo questing as a warrior isn’t the most fun, but chances are there are going to be times when you’ll want to do it. I’d say go Arms until you start to notice difficulty tanking, likely high 40s, low 50s, and by that time, you’ll know if you want to mix it up by questing/grinding or just doing dungeons.