travelingbard,
It's really a toss up in many circumstances. ANY MOTOR HOME can cost you in repairs/maintenance, upkeep, whatever you want to call it. By design, most diesels will be built on heavier chassis and, therefore have heavier components which simply means, heavier duty for longer lasting and, for the most part, better riding.
Most gas units are built on lighter chassis and, therefor ride a bit harsher and have lighter duty components (chassis parts, wheels, frames, and a few zillion other parts and components). But, they might cost you a bit less too.
Owning and operating a diesel doesn't mean you have to sell your first born either. Yes, many have larger oil pans which means MORE OIL than gas engine will hold which means a tad more cost on an oil change. But, on that same thought, many mfgs of those diesels recommend some pretty serious mileage between those oil changes too.
Your brakes on most diesels will outlast the brakes on a gas class A due to at least one primary reason. And that is because most diesels come with either an "exhaust brake" or, a "Engine Brake". Both of those are auxiliary braking systems that enhance braking while if used correctly, will double or even triple the mileage/time/duration between any brake maintenance/overhaul.
I'd say that about 98% of the diesels out there that have drivers that know how to use their auxiliary braking, will get way over 100K to 150K miles before even thinking about replacing brakes. I know our '04 Itasca Horizon 36GD with the C-7 330HP CAT is sitting at 60K in mileage and, those shoes (all four wheels) almost don't even look like they've been used.
And, some of the "HP" quotes that have been stated on here are a bit off. I have several friends who have the model 34H Winnebago Journeys and Itasca Meridians who have the C-7 350HP CATs in them. Those are outstanding engines. Yes, CAT did drop out of the "over the road engines" market back a while ago due to smog compliance issues but, those engines are very well supported all through out the U.S.
You will never find any trouble obtaining parts and or service on those now, or in the future. As for the "no service records" on the Adventurer, that's not the end of the world, not by any stretch. If you're not all that mechanical and, other than your uncertainty of the maintenance, if the floor plan and condition of the coach is really to your liking, then simply drive it, use the brakes, climb some hills, check it out in all the departments, i.e. lights inside and out, water pumps, generator, 110 outlets and all that stuff and, when somewhat satisfied with what you've seen and found, then take it to a qualified tech of your choice and ask for a good investigation into the drive train and or chassis.
Winnebago has a pretty substantial reputation for being customer oriented. There's a zillion folks out there that are really happy with theirs and, many have had the need to call Winnebago Customer Service for this and for that when it came to technical questions on their coach and have had pretty darn good results from the folks at Winnebago.
Winnebago and Itasca both are fiberglassed roof coaches and most, if not almost all who own them, prefer those roofs way over the other styles like rubber. They're much more resistive to damage and deterioration.
One more thing. The interior noise level on about 99.999% of the diesels out there are considerably quieter during traveling due to the fact that the engine is over 32' or more (usually the minimum size for a class A Diesel) you.
But, the main thing is, the floor plan. Make sure it's really what you want and desire. The interior design, cabinetry, ceiling material, flooring, and more will make a pretty good impression your decision. Good luck.
Scott
