In laws bought an older diesel pusher without any experience and they got taken to the cleaners. All sorts of issues including engine, tires, brakes, starter, leaks, etc....it was a financial burden for them and although they bought what they could pay for cash, they sold less than a year later after dumping a ton of money into it as no end in sight.
Pretty sure it ruined the idea of an RV for them...they would have been better off buying something newer with a lower total cost, so just something to keep in mind. Take a good look at everything and weigh the pros and cons. I would recommend driving the units you like to see how much the difference is worth to you.
There are a lot of gas MH on the road, and engines and transmissions have come a long way. A new v10 engine is a lot cheaper than many problems a diesel can have. To say not to even consider gas is not accurate in my opinion, as depending on use and maintenance budget it might actually be a better option.
I would take an immaculately clean and well maintained unit over an average maintained better name unit any day, so I wouldn't jump into one without getting a feel for history and usage as well or how many owners they have had.