Basically they all make really good trailers and they all make lemons. This is true from the cheapest pop up to the most expensive motor home. Pick a trailer that you like the fit and finish on as well as the floor plan and then really really inspect it prior to taking ownership.
Now that said, most trailers are not designed with full-time in mind. There are a few 5ers that do list themselves as a full-time rig but those that don't tend to void their warranty if they find out you full-time in it. (i.e. don't tell them you use it full-time). What you really need to find is a trailer that has a manufacturer that really stands behind their product. Not to mention a good dealership. Jayco and forest river tend to have a pretty good rep with this. Crossroads is trying to regain their rep. I believe heartland has a good rep too but from what I understand some of the former management from crossroads has gone to heartland (the team that caused crossroads to lose face with its customers).
I can tell you the sabre line is really nice. We almost bought a sabre tt but got the sabre 5er instead. Our zinger tt was an entry level tt that performed well.
The key to a tt or 5er is to make sure you have plenty of truck for whatever trailer you buy and then get a good hitch. If you don't have a TV yet then figure out exactly what trailer you want first and then buy a truck that is capable of handling its loaded weights. For the size you are talking, I would be looking at 3/4 and 1 ton trucks to do the job and with full-timing you might want to consider diesel. Pay close attention to payload on these trucks as that is frequently your weak link. Happy hunting and enjoy your soon to be retirement.