It's funny. When I first started looking for a bus I wanted a gasser with a 4 or 5 speed. I figured I could fix a gasser myself since that's what I have experience with and the 4 or 5 speed would be just about bulletproof. Now I own a diesel with an AT545
I guess it just comes down to personal preference, but as I read I quickly learned that a diesel was probably the best bet in terms of mileage and such. I won't use the bus often, but when I do it will be for long distances. I also like the resale (not that I ever would sell it) value of a diesel. There is no doubt in my mind that I will get what I paid for it should I ever decide to sell.
As for the auto....well.....a 4 or 5 speed is hard to find. On top of that, I drove a buddy's bus (he bought his the same week as mine coincidently...we had not talked about it previously) up Minnesota's infamous Highway 38 from Grand Rapids to Marcell. It is a narrow, windy, hilly road frequented by logging trucks mostly. In 14 miles it goes around 10 lakes (we are the Land of 10,000 Lakes after all). I got so annoyed with shifting that crashbox and 2 speed rear after that one trip that I decided that I would have an auto. I've never looked back.
For as much hate as people seem to have for the AT545, it's not a bad tranny IMHO. It was used for well over a decade and for millions and millions of skoolie miles as well as in other medium duty trucks. Sure it has its flaws, but they are reliable and hold up. When they give up the ghost they can be replaced cheaper than the 4L60E in a half ton Chevy truck. On top of that, anyone can drive a rig with one. Anyway...enough ranting....