Advice on Class B purchase process

[sbslider]

We are considering buying a class B vehicle. To narrow things a bit, our primary focus in a vehicle is 18-22', bathroom in the back, and possibly new but more likely 1-3 years old. Some things I'm wondering are:

New vs used in terms of warranty? Sort of thinking one that has been on a few trips has warranty issues worked out, but is still new enough that things should fail for a bit.
How long do manufacturers warranty's last? Are the transferable beyond original owner?
Dealer vs private sale? things to look out for on both?
Somewhere I saw its good to avoid manufacturers first model year vehicle, as they haven't worked out the issues associated with a new build yet. How would one find how long a particular model has been in production?

Partial list of models on the top of the list are:

Entegra Coach Ethos 20T
Jayco Swift 20T
Thor Dazzle / Twist 2LB
Thor Sequence / Tellaro 20L
Winnebago Travato 59K

What's the difference between the four Thor models (besides $10K of MSRP)? The floor plans all look the same

Thanks!!