We have own a Dutchmen and a Keystone Springdale and now a Keystone Outback. We have been very pleased with all 3 trailers. I think, today's campers, especially the brands you've identified are pretty much equal. I think the real difference is the follow-up service you get from your dealer in the event of a problem, and more important, when your camper goes out of warranty.
Personally, we've never had any problems with service for any of our campers. But by far, the last dealership we used, when we bought the Outback, far out shines the other 3 (pop-up included).
I feel confident that Dutchmen / Keystone are adequately good products and their manufacturers do stand behind their products. And I honestly cannot compare with any other brand since I've never owned anything else. I think the problem so many have are with their individual local dealerships, not the manufacturer or warranty services.
All brands being equal ... (um ... my opinion ... get an Outback! ... real wood, good quality, and they are having a strong come-back in sales after a few years of slump.)