A DP'er typically has several advantages over a gas unit.
1) much less engine noise going down the road.
2) better ride due to air suspension
3) much higher carrying capacity due to chassis being designed for the MH it's built on.
4) higher quality interior with better cabinets/furnishings, real wood in lieu of paper wrapped.
5) higher towing capability
6) much more/better outside storage
Just a few items I though of! And yes, everything on a DP'er is more expensive. Initial cost. tires, oil changes, filters, fuel, and, in genial, most repairs.
Now, knowing all that--what would I buy? Hands down, the Diesel pusher!! In fact I did, 3 times even. A Gulfstream, a Monaco Dynasty, and a Allegro Bus and we luv'ed driving and camping in every one of them!
Days camping (2015)----88 days
Days camping (2016) ---110 days
2016 Wildcat MAXX 28RKX (33' TT), 2007 13' Scamp
2015 Ram Laramie Hemi
30 years RV'ing
12 different RV's