That 3170DS is a Bunkhouse model. Helpful with kids, maybe not so much once they move out or want to go on vacation with somebody other than the parents. My guess is that the overall expansion of RVing as a pastime will allow resale of bunkhouses without a price penalty for that feature. But that's just me.
The Sunseeker in the ad has more features than the 28A's on the CruiseAmerica site. Also about $20,000 more than the same year 28A's with twice the miles.
It's probably true that the Thor Four Winds that go to Cruise America are spec'd to reduce problems. Commonly, rentals don't have Carpet, or Ladders, or Awnings. I don't know if the actual construction is beefed up also, or not. I can say, I don't hear many complaints about the "Majestic" brand, which are retired Four Winds from CA's fleet. There's a rental outfit in Anchorage that claims to be top line ultra premium. They used to rent only Winnebago coaches in a rental line called "Chalet" which they ordered to their specs. Now they also rent Thor coaches. I like to think Great Alaskan Holidays picks their fleet carefully, so I take it as an endorsement of at least part of the Thor line. Great Alaskan sells their fleet off much "younger" than many other rental outfits, and the units look like new.
But I digress.
The issue reminds me of the scene from Smokey and the Bandit where Big Enos is peeling cash off his bankroll so Bandit can buy a fast car. Bandit looks a the money he's got so far and says "Faster." Big Enos hands over more cash. "Faster than that" and more cash. Not only is this Sunseeker much larger than the last one you mentioned, the price is higher. Floor plan looks like you can function fairly well with the slides IN. So, How Fast do you want to go?