aswagerty14,
Welcome to the Forums! Is this your first RV you're looking to purchase?
As a few others have noted, I'd put floorplan above just about any other deciding factor, except condition, of course. Do both of the units you're looking at have the same floorplan? If so, then you can nit-pick at other things. If not, you need to carefully study each floorplan to see what will work best for you. Some examples: There are split-baths and all-in-one baths. If you have kids, I think the all-in-one baths are a better option. But if it's just a couple, some prefer the split-baths. Some rigs have bath and a half. Some have sofa(s) and a dinette. Some have free standing table and chairs in stead of the dinette. Some have a sofa and/or lounge chairs. Queen bed/kind bed/bunk beds/drop-down bed? Which cabinets and drawers are inaccessible when the slides are in? (Important if/when you're travelling on the road and can't extend the slides.) Lots of things to consider. These are things that IF they're not right for you, will wear at you much more so than a few mpg difference. georgelesley said it best above "If you or DW, especially DW, do not like the floorplan your fuel mileage will be unlimited since you will not use it for very long and it will just sit in your yard." And one other thing to remember is that in many parts of the country and at different periods in the recent past, diesel fuel costs more than gasoline. So the extra mpg diesel delivers may be offset somewhat by the added cost of the fuel.
Have you been able to drive each of them? It's usually the driving experience that sells folks on the diesel over the gasser. If you're just looking at papers & websites, you are doing yourself a disservice in trying to decide between gas & diesel.
There ARE substantial differences between a DP and a gasser Class A motorhome, but like many others have said, I wouldn't make the decision on mpg differences.
Good Luck in your decision, :)
~Rick
