I think the usual thinking is that automatics give you more control and consistency of the torque being applied. Right off the bat however, the manuals have a higher crawl ratio (84:1). In low gear, the manual rolls without even having to hit the gas in first gear. But in 4H, you have to feather the clutch to get going, which can wear it out. Personally, I have a manual because I think its more fun to drive all around
Gearing and transfer case will make a lot of difference in a manual in trying to crawl an obstacle in low gear. I went auto on my last 2 jeeps because it's just one less thing to worry about when I'm trying to focus on other things. I've always got manual mode with the auto when I dont want the jeep shifting.
Just like in street racing automatic for the win , crawl ratio is a non-issue with a Rubicon automatic. The new 8 speed auto has a low first gear add in the Rubicon transfer case with its super low crawl ratio combine that with the control of the automatic and it’s hard to beat.