This is definitely going to be an opinion question and everyone's experience will vary.
Every Forest River camper we've owned (3) have been outstanding. I'd highly recommend them and would love to own an XLR. The only Heartland product we've owned was a 2011 Cyclone. It was a piece of junk and dealing with Heartland was terrible.
No experience with Keystone or Dutchmen.
I think having a great dealer is just as important. The one we deal with primarily, helped us keep our sanity when we went through our Cyclone nightmare. After the Cyclone, we bought from them again and hope to continue to do so.