We've really enjoyed our 34' and would find it difficult to go any smaller. With the exception of one occasion, we've not had any trouble getting in and out of filling stations (the one time involved actually unhooking and repositioning the truck). Typically a good idea to plan routes and, most especially, turns in advance, and anything which might create a tail dragging situation. Beyond that, it tows wonderfully, plus I like having two additional braking wheels with the third axle. Very easy to back up - I can typically put it right where I want it on the first try - even in the dark.
I also like the fact that you don't see the long long trailers on the highway as much as those 32' and under. Get more gawkers.
I don't know what year model you're considering, but if you are serious about a 34', a pre-widebody is about all you'd want to take on with your current truck, and I believe that would be right on the borderline. In contrast, a 3/4 ton with a Duramax/Allison combo, or even the ZF-6 manual, and I'd think you'd be just fine.