Previous comments pretty well sum up this long debated, tired subject - Diesel will have more capacity, better ride, but comes at a very high price both in initial cost and maintenance. Gas MH is much easier on the budget, but won't ride quite as nicely. They are pretty much the same when parked.
And, the previous poster is exactly right - Floorplan is very important, in some ways more so than what kind of engine, chassis it has.
Floorplan is actually the main reason why I prefer a gasser MH. I absolutely HATE having the door in front of passenger seat, something you're pretty much stuck with on most diesel MHs. Makes it feel like you're driving a big school or tour bus, hahaha! I also really, really like having a window on back wall of the rear bedroom, something that you cannot get on any diesel pusher MH. Between those two floorplan issues, diesel is pretty well eliminated for us, before we even start talking about the huge $$ difference or the horrible smell of diesel fuel I want nothing to do with.