The gas vs diesel thing will always be a long debate with everyone picking sides.
What it comes down to, is some people are just uneasy when they see an engine roaring at 4800 rpm. It's true that horsepower is horsepower, it doesn't matter how it's made, two engines will move the same at their rated hp levels. The feeling is that the one spinning 4800rpm is somehow less powerful than the one spinning 2400 rpm. It is less powerful, at 2400 rpm, but at 4800 it makes the exact same work as the other engine.
Most people aren't willing to wind up the gas engines for prolonged periods of time, and thus they are viewed as weaker. There are 2 other issues that come into play too; one being that engines are most efficient at their peak torque, and will thus usually get best mileage figures at that rpm; and on diesels this is a lot closer to the peak hp than on a gas engine; thus your diesel engine has the advantage of being at 60-80% of full horsepower in its sweet spot, whereas the gas engine is at 40-50% tops (a v10 at 2200 rpm isn't exactly something to write home about). There are however plenty of gas engines that make it just fine to half million miles or more, far more miles than you'll ever see in an RV.
The last advantage diesels have over gas, and unfortunately it's an advantage that has somewhat eroded in recent years, is the lubricant property of diesel, meaning the piston gets some form of lubrication from the top as well as the oil on the bottom. This was in the past a huge boon, and one of the main reasons the old diesels were known to outlast gas engines. The downside is that, with ultra low sulfur diesels, a lot of that lubricity went away from the fuel.
In conclusion, the V10 won't die if you run it at 4000+ rpm for long periods of time. I've had 2 of them, worked them hard, and they will take the rpms all day long. As long as their oil pump doesn't go out (extremely rare), and they aren't starved of fuel (stock tune is very conservative in this aspect), they will run for a very long time. If only they made them with dohc heads, ti-vct, and direct injection, we'd have some very happy motorhome owners... But at that point Ford wouldn't be able to charge 8 grand for a diesel in a pickup anymore.
To the OP, the engine you pick will influence your drive to the camp site and back. If you're a weekend warrior, and i know what you mean about living in a hilly area, get the biggest engine you can find/get in your coach, and that your wife will let you get away with
. If you're gonna go out to a camp site and stay there for a while (aka you're retired or have mass amounts of vacation), then get the best coach you can for the money and don't stress the engine choice too much.
I'm a weekend warrior, I bought my first rv as a diesel pusher because I thought if I didn't like the power I could bump it up a bit... well, I can, but the trans won't take too much more. Now that i know I like it, and know what to look for in the next coach, I'll buy my next RV with something with more cojones though. Not that I can find something with less power than my 190hp cummins