Do you plan to snowbird in just one location or will you be moving frequently? The reason I ask is that a tag axle coach (much more money) is a great advantage to those to plan to do lots and lots of driving over the course of the year but no advantage to those planning to move from point A to point B only a few times per year.
No advantage? Even if the coach is rarely driven, is a tag axle not an advantage during those drives?
The dealers at the Tampa show take trade-ins. I would think that after the show they would have a lot more used inventory than at other times. However, a dealer is not the only way to buy. Do not overlook buying from individuals. The price may be much better and you can find out more about the unit's history from the owner. Try websites such as RVT.com and Rvtrader.com.
Nothing to be afraid of. Diesels are at least as reliable as gas engines, probably more so. They run hundreds of thousands of miles in trucks and busses with no maintenance except fluid and filter changes. Yes, more expensive to fix but they hardly ever need fixing. The driving experience in a diesel is far better than in a comparable gasser.
I had a Beaver with 8 airbags for ten years. I traded it a few years ago for an Entegra on a 4 airbag Spartan chassis. The Spartan chassis rides far better, and handles just as well or better, so I don't miss the extra airbags at all. To be fair, the Beaver was 40 feet with no tag, and the Entegra is 45 feet with a tag, so the comparison is not a direct one. But my point is that eight airbags are not needed to make an outstanding chassis. Witness all the high end Newmars, Entegras, American coaches and others on four airbags.
While DSDP Don's post may sound harsh, he is right about the need to "kick the tires". You must narrow down your choices to a few models, and then go through them and imagine living in them. Try everything you can, open every cabinet, sit in every seat. Examine the storage bays and the tank capacities. Check the levelling sytem, operate the slideouts. Sometimes it is the little things that can tip the scales. A great way to do this is at a major RV show such as FMCA nationals, Tampa Supershow, or the big annual show in Harrisburg PA where you can directly compare one model versus another. When I bought my first motorhome, I flew half way across the country to do this and it was well worth the time and money spent.