The detracting attribute of a dome shape is the interior space lost in the curved wall to the outside. It's the same sort of space lost in a curved teardrop profile as it slopes to the back, or the rounded front. With a dome, you're losing interior space in both length and width.
I'm noticing this consequence of curved profiles in some designs I'm noodling with for a 40x48 trailer:
The left-hand one is just a simple radius curve on the front, the right one is a back-to-front slope similar to jbyrd's Go-Camp. In the slope profile, I can't scoot the figure as far forward as I can in the simple curve profile. I like the slope's look better, but there's more room in the other, and that's important for a small trailer. Well, at least one my wife will want to climb into...
The dome shape can be very strong, but I think the lost space kills it for a small trailer...