Two more things to consider is your travel style and the availability of diesel mechanics in your area. If the majority of your trips will be short-range, you may be better off getting a gasser. They are lesser expensive to purchase and lesser expensive to operate and maintain. Gasoline engines have gasoline mechanics pretty much everywhere; however, diesel mechanics are not that plentiful. Diesel is definitely the way to go if you plan to do higher mile trips including mountainous terrain and/or towing. Diesels like mileage and they have better torque for towing. But for a few 500 mile trips per year with a moderate toad, IMHO, I think you'd be better served by a gasser.
As far as amenities, the sky's the limit for both gas and diesel units. BUT...for the most part, the more expensive amenities are put in diesel units for yard stock. Marble and granite counter-tops, tile or hardwood floors, solid wood cabinetry and high-end furniture, chandeliers all weigh a lot, so they are usually reserved for diesels with more power to spare. Plus, the clientele that usually go for all those higher-end things may be planning on full-timing so they are willing to pay the extra money for the luxuries.
And, although you might get a couple extra miles per gallon of fuel on the diesel unit, you will pay extra for the diesel fuel at the pump so the difference is lost anyway. Lots to consider, but as many have said before me...pick out a floor plan you like first, and then choose what type of pusher you want. You'll spend a lot more time inside the coach while it's parked than you will driving down the road. Gas engines will get you there the same as a diesel... regardless of the trip, but you might not win the race up the hill.... ;-)