I thought MT's were supposed to be better on rocks than AT's anyway, not just mud. I'd say go with MT's, then you'll be covered in all situations. I've been pretty happy with my MT's, and you never know when you'll encounter mud on the way to the rocks!
yea i agree go with MT's all terrains are okay if your going for good looks and good on road drivablility but go with the muds if you really want to play off road and you can stand not so great on road manners.
I have both BFG MT's and AT's on my vehicles now. I wish I'd skipped the MT's. 95% of my driving is on road and the ride is terrible with the MT's. The MT's are wearing faster. For me, the AT's work just fine. Also have two sets of MTR's. Like 'em.