A warrior in your team means more "complex" tanking in comparison with a Pally/DK

It is a lot harder to keep AE Aggro with a Protwarry (Shockwave made it a bit easier but consecration > all)

On the otherside a Pally gives you all the nice auras/buffs - warriors only provide the HP Shout...

In my oppinion its a personal flavor, which class you want to play, but i would prefer the pally !