The 310, 325, and 345 models are probably the most common. There are a fair number of 28' and 30' ('300' series) units around. These units are surprisingly easy to drive. Just ask Doc Joe ('winner') who is eighty something driving his 345 around the country. My wife drove our 345 around town (soccer practice, my office, and home for loading) one day on some pretty tight roads.
Most all of these units are on the Chevy P-30 chassis with a Chevy 454 engine so they all have the same issues and drive very similar regardless of length.
The 79-81 Excella 28's can be polished up all shiny and nice!
If twin beds are acceptable, you will have lots of 310's to choose from. The 310's with large rear sleeping are harder to find but out there if you look hard enough. Oh yeah, 280=28', 290=29', 300=30', 310=31', 325=32.5', 345=34.5', and 350=35'.
The 270's are great units but lack a rear sleeping area and bed. You sleep on the fold out sofa's.
My advice is to compare an older AS MH plus some fixin' up money to the other units you are looking at. In my opinion, spending $20,000 + $10,000 for fixin' up is far better than $30,000+ on some other brand that won't last very long. By fix-up, I mean new air bags, AC units, fridge, tires, engine tune-up, belts, hoses, etc.....