I guess my initial thought is none of them are perfect. We have owned two different brands of fivers, Keystone Montana and now a Heartland Cyclone. The floor plans we have had are the larger models (39' to 44') with MSRPs in the $100,000 to $125,000 range. I have found that these have had larger frame rails and the side walls seems to be constructed better. We have had minor issues with all of them but nothing major.
I would first find a floor plan that you like in a model that you can tow with your current truck. Then start doing a little research on the history of that specific make. Owner's forums can be a good place to check for common issues with certain makes/models.
We have had our Heartland for just a few months. We are very happy with our purchase. I only have two issues that need fixed under warranty and might be difficult to get done as full timers. Our ice maker doesn't work (LG frig) and one of the fantastic fans is detective. Since I can't easily take it to my selling dealer (1,300 miles away) I will have to find another dealer to do the work which is sometimes almost impossible. The Heartland factory won't do warranty repairs unless it is something really major that dealers can't handle.
Oh, and by the way, if you are looking at new dealer stock on a fiver you want to start negotiations around 32% to 35% off MSRP. Be sure to locate the exact make/model/color you want at several dealers around the country before you go to the first dealer and start dealing.