The tougher the trail, the better your Jeep will do with an automatic. Pro/competitor offroaders & rock crawlers went to automatics years ago... more low-end torque and far greater control with an automatic. I convered my well built (f/r lockers, etc.) '97 from a 5-speed to an automatic several years ago and going to the automatic gave nearly the same boost in offroad ability that adding the pair of lockers did.
Go to a major rock crawling competition and you'll see that most of the competitors run automatics.