Thor appeared to be the first (of recent years) to mass market the front overhead drop down bed in a class A. Makes for a bit more family friendly rig with the additional bed rather than a sleeper or jack knife sofa. Since then a few other manufactures have introduced a similar feature such as the Forest River FR3.
You won't find a class A gas coach built in the last 5 years or so with a GM based power train. GM discontinued the Vortec engine which left only Ford producing a chassis. I wouldn't worry about what is under the floor of the coach. The F53 chassis has been a pretty reliable frame to build on. Just ensure whatever model coach you lock in on has the weight capacity you might need. There are a couple of models built on the smallest F53 chassis available which really limits how much stuff you can pack in and not break thru the GVWR limit.
Regarding quality control of the current builders, each has gotten a couple of black eyes. Can't say if Thor is the worst of them but they do build a lot of rigs. My coach is a late model Thor product and haven't had one problem as yet with any of the Thor provided material used in building of the coach. Judge each coach individually and don't be distracted but the sales rep. Open all the doors, drawers and such. Do a very detailed inspection of a prospective coach from the floor to the roof.
The question of new rather than used is about like which is better Coke or Pepsi. I recommend something used maybe a year or two old. You'll still have a bit of the original warranty available while the first owner took care of all the QA issues during the first couple of months of ownership. Plus stepping back a few years might get you a step up in coach size for the same price as new.
Don't be overly concerned with the entry level rubber stamp either. The coach builders still use the same chassis, same fridge, same water heater, same air conditioners,,, as the higher level rigs. You will find the interior cabinets will be made of lighter material or maybe the seating isn't covered in actual leather and such. One advantage of the lighter construction materials is you have more available weight capacity for your stuff.
Good luck with your search.
