Vandwelling in a beast-wagon vs. a standard conversion van
Vandwelling in an extended body van (aka 15 passenger) with a hi-top is different than living in a standard length camper setup. The tall fiberglass shell makes the inside feel truly spacious. Relatively huge, in fact. The shell also weighs a lot more than the hi-top on a standard camper, being that it is at least twice as tall, and also several feet longer. The extra length on the extended body makes it possible to store bicycles and a bike trailer in back without sacrificing any living space as compared to a standard length, or 12 passenger van.
The extra size and weight are most noticeable when driving slowly on uneven surfaces. Our van will rock and sway over potholes and speed bumps. On the highway, though, everything feels basically the same in normal conditions. Fuel economy is comparable: bad vs. bad... to me, all other factors are more important. (If you need excellent fuel economy, you should consider squeezing into a minivan, or driving less.)
I was intimidated at first by the prospect of buying an extended body van instead of a standard length. My first worry was that it wouldn't fit in a standard sized parking spot - and it might be harder to parallel park. Nervous forum-dwellers point to the reputation of a 15 passenger van to roll over or be difficult to drive in windy conditions. Neither of these factors ended up being a problem.
The van has never been difficult to fit in a standard spot. Parallel parking was easy to get used to. Sure, there might be a spot here and there that a standard van would fit, but ours would not - but in practice, I haven't even seen that happen yet. The big van requires a little more attention when driving in high wind - but again, I don't think this is a big enough factor to dissuade a prospective vandweller from ownership, other factors held constant.
Being a married couple with two dogs, I feel certain that we made the right choice. We have more space than a standard size van, and the weight/handling/MPG penalty is paltry. I'm thrilled about the aesthetics of our home as well. I don't like owning fancy things. I don't like to tiptoe, walk on eggshells, or fret about scrapes. Our home is reasonably low-key enough to park on the street, but it is not without personality. The casual observer will only see an old passenger van. We're having a party, but it's not out of hand.
Other vandwelling vehicle options
Older VW Vanagons and Westfalias are popular. They're too small for our big pack, and it's my belief they scream "lived in" when you see one with curtains on the street. Those tent-tops are neat, but you won't put those up when you're parked just anywhere.
Some people convert short school buses or a wide shuttle bus. I'm a little jealous of the extra width of a shuttle or school bus, but I am more interested in the ability to park in the maximum number of locations. Anything longer than our van would be hard to fit in a standard parking lot space, and might fall into the "oversized vehicle" category of local ordinances, making street parking a challenge. Again, I feel confident that our van is perfect for our exact needs.
Everybody needs to consider the relevant factors before picking a vehicle to live in. Most of the time, I think a standard length van is the right choice, and I would always prefer a fiberglass raised roof. My previous van - a 1990 GMC conversion van - was great. Now that I have more people and dogs in my dwelling, I am glad to have a longer body and higher roof - but at least for now, I would not want anything bigger.