This is a subject where you stand where you sit. If you look most posters are recommending that you get what they have. People who have big, nice rigs generally have diesels while those who have more economical rigs generally have gassers.....you need to decide for yourself what you want. For $70,000 you can get a very nice used diesel with a high quality house, which is what I prefer. YMMV, but my thought is that to enjoy being in the coach for months at a time you need to have a house that's nicer than the house you have at home, or else you'll want to get back home to your nice tv, bathroom, and kitchen. The Beaver Monterey you looked at is a mid-level diesel, and doesn't have things like Aquahot water and house heating and air levellers, but does have a rugged power train and running gear which will last better than any gasser unless you are a very gentle driver.
Bottom line.....for me, a diesel is what I want.