Well, we are biased because we have owned 2 Drv's. We had a 2007 Drv Select Suite that we lived in for 5 1/2 years. It was a great fulltime unit, held up well, good factory support. We have now owned and lived in a 2012 Drv Mobile Suite for 4 years, same comments. My biggest issue is that Drv tried that Schwintek track slide system on the 2012 and early 2013 models. We had to have it rebuilt at our cost, $2400. At the national rally last June the factory rep told everyone how the factory would continue to stand behind these units. Uh no. I would still buy another Drv, a quality product.
Spacecraft and New Horizons, as you say are few & far between due to the high cost. You may have trouble getting a dealer to work on it when you need a repair. If they aren't familiar with the unit they tend to decline. And there will be repairs, on any unit. Forks are so new to the market, comments would be the same, except that there are no used units out there. There's a Drv dealer in Elk City, OK that is going to carry the Forks but after many months of advertising them on their website they still don't have a model to show. Rolling Retreats. Tetons are good rigs but are getting old, there are still some good units out there.
You are smart to look for a good quality used unit. My 2 cents, don't try to find the perfect unit, no such thing, you have owned a MH, you know that. Look for owner's forums like www.suitesowners.com
. Actual owners are going to be your best resource. There may not be one for Forks, New Horizons, or Spacecraft.