I just looked at the build sheet the original owner emailed to me when I bought my van in 2006 and what do you know .... I have 3.8:1. I have always been impressed with the "crawling" ability of my van, so another vote here for 3.8:1.
Add another vote for the 3.8/1. The additional torque multiplication's not as important, as I doubt anybody's going to be climbing 45 degree slopes in a 10,000#, expen$ive behemouth, but on really rough stuff, being able to idle up one side of a rock and down the other doesn't rattle the dishes nearly as much as going faster.
John T