IMHO, I would not put much weight in the Polar Package hype. More for marketing then anything else. A heated basement just means they run non insulated flexible dryer duct through the space.
There is only so much R factor that can be in an 1.5 inch thick wall and roof. BTW, when you open up the door take a look at the wall thickness. Not all RV's are created equal.
If you can look for dual pain windows. This will cut down on the heat loss and condensation which can be a real issue at times. High ceilings mean you need to heat that space also, a fan can only do so much when it is flush mounted.