I own a 31 foot Gasser with a V-10 and am satisfied with it for short trips and I even drove it around the country on a 7,000 mile loop once. It did fine in the Western mountains, even towing.
My biggest problem was the air conditioner and other non-engine related problems. My point is (like so many others have mentioned) your engine choice is really not that important for the miles you plan to drive.
I am in the process of upgrading to a 600 HP ISX15 in a Newmar King Aire, but the engine was dictated by the coach, not the other way around.
The reality is that the Ford V10 is an excellent proven engine these days and will provide you years of great service and good performance. You have no need to worry about that.
It is definitely louder than a diesel pusher and your ride will be rougher, but since you aren't going to be driving that much, it is probably not worth worrying about. Now, if an additional $25 - $40k isn't important to you, then by all means, lean towards the diesel.
Find the floorplan that works for you and choose a brand you have confidence in with the quality level you want and you should end up being fine.
