the way i see it, the hunter will roughly do the same dps regardless of wether or not your going to tank or not.
on the other hand, a pally will have a huge difference in DPS.
i would let the pet tank, as the only real diffence for the hunter is wether or not growl is on, and you spec ret for DPS.
the hunter should be able to keep his pet alive better then you can keep your self alive if your tanking. and you can help keep his pet alive, where as he cant help keep you alive.
all in all, the pet acting as the tank has far more benefits then any other set up.
and the fact that he she is going BM will make the pet all the better tank. mostly because of agro stuff.
im working on a hunter right now actually. and my cat, a dps pet not really a tank pet, tanks her way through some rough encounters just fine.
Edited, Dec 10th 2007 4:04pm by RuenBahamut
Edited, Dec 17th 2007 1:13pm by RuenBahamut