JAD, there is a lot of personal preference in choosing how to configure a camper van so you will need to filter through all of the options to what works for you. Storage room will increase a lot with the longer wheelbase, that extra length can limit you when parking and maneuvering, I travel with my wife and looking at the short wheelbase it would seem too small for us after seeing how we can load up the long wheelbase Sprinter. If you want air conditioner then you usually need either campground 30 amp power or a generator. I plan to go without the AC this time since we have only used it a couple of times in the three years we have had it. We avoid high heat and humidity by avoiding it in our travels so it works for us to be without AC. A good place to look at all the configuration options for beds, couches, etc., is the Sportsmobile website where they show just about all the possible ways to configure the layout. I always liked the penthouse pop top (not sure they will do one on the low rood transit) but my wife would not have it so I expect we will go with the high or mid roof depending on how they feel when we go inside one. Storage will be tight in all camper vans so you really need to consider what you want inside vs outside like bikes. Many people have a raised bed platform with lots of storage underneath for things such as bikes but then the bed tends to be fixed in place which we wouldn't like because we like a couch of some type when not sleeping. Again, too much personal preference to tell anyone else which is best. I would suggest you start looking at any camper van you can find just to get an idea of what would work for you.
We are very happy with our Roadtrek and it has been a reliable vehicle. Keep in mind that the main customer for the Sprinter camper vans from Roadtrek, Pleasureway, Winnebago, etc. is looking for a high end model with nice interior and all the options. These vehicles are not designed for much beyond great handling on the highway and comfortable accommodation when parked. They are starting to address the need to camp away from hookups but it is difficult to go very far from a reasonable paved or gravel road with all of the stuff mounted under the vehicle (generator, black and grey tanks, propane tank, plumbing with macerator, etc.) resulting in no ground clearance and easily damaged components.
Based on my assessment, we have been lucky to get a pretty reliable Sprinter. I read too many stories about Sprinter problems to think they are all as reliable as ours. I think the Sprinter has too much technology that is prone to reliability problems. I used to work for Ford so I do have a bias towards something from them.
As I said, we have seen lots of places we would like to go that require a vehicle designed for bad roads. We can give up some if the high end design stuff to get a more rugged vehicle.
2008 Roadtrek RS Adventurous