I have the 18EC. They are a little heavy, at 5150 lbs dry, but it's also built much more substantial. They have an aluminum roof and the corners are protected by wrap-around aluminum edges.
I mainly bought it because, with the loading ramp, it's easy to load, unload, and clean. I also like the simple floorplan.
Everything about it seems built stout. The floor is covered with a heavy-duty spray-in covering, kind of like a spray-in bedliner.
The garage floor does include space next to the kitchen cabinets, so it's not built to put a tremendous number of toys in it. But it will hold a some of the smaller side-by-sides, such as the Polaris 500, and Razr. It will also hold traditional quads, motorcycles, bicycles, canoes, etc.
I was towing with a 2004 Tundra, and it was a little underpowered, and probably either at or a little over the payload capacity, although I still used the truck for several trips. A newer, heavier payload half ton would be better. I opted for a 2009 F250 I found at the right price to pull it.
All in all, I am very pleased with it so far.
Here a few pics:
