Having friends back home in brissie that used to compete in 4x4 (both manuals/autos) events i cant really say which is best. They both have their pro's and con's.
I prefer Auto myself after much contemplation. For one, i cant stall it. Ratios take care of the jeep wanting to take itself for a ride down a steep hill. I feel i have more control in an auto over a manual.
It all really depends on what you want to do with your new Jeep when you get it. Good luck in deciding!