I say DW.
Noone is going to get mad at a DW warrior (especially a DW OT warrior) for wanting [item]King's Defender[/item], [item]Spiteblade[/item], or [item]The Decapitator[/item] - but those would be weapons that are very useful to you not only in DW but also tanking (as aggro weapons).
There's just a nice synergy between Fury/DW and tanking if you ask me. Too many Arms talents are all about the 2h; a total waste while tanking. But precision, enrage, death wish, flurry, blood craze, improved demo shout, even improved cleave all have some tanking utility. And many of them are deep Fury, while the "arms tanking" talents are first two tiers (tclap, heroic strike, parry).
[item]Royal Cloak of Arathi Kings[/item] - arguably the Fury cloak in Karazhan, also makes a fine tanking cloak in the right circumstances.