You have to decide how big you need it to be for the amount of time you are using it, and how much you want to pay, for both the RV and the vehicle that will tow it.
My local dealer can put me in a new 14 foot travel trailer for about $12,000, but if I were going to be in it for three months in a warm (not hot) place, I would probably go 19-footer for about $15,000. Either can be towed by my one-ton passenger van. If I had a second person living in it, I might want more space, but too much more space and I need a bigger tow vehicle.
Want a lot more space? Moderate size, low cost fifth wheels, maybe $40,000 for a 28-30 footer up to about $70,000 for 38-footer (getting into 1-ton dually pickup territory).
That's decent quality, low price brands. It goes up from there. If you want a new Hitchhiker fifth wheel, expect to pay about $110,000 for 35-38 feet. If you want the quality of a custom-built Excel or New Horizons, you can easily double that. But I wouldn't pay $200,000 for a fifth wheel I was using only three months a year in a not so challenging climate.
I've been around RVs, shopping and using, inspecting what camping companions buy, and I don't really see any brands to stay away from. It is all a matter of how much you want to pay, as the lowest cost models fit most peoples occasional use purposes, mid-range is fine for seasonal and even long-term use in moderate climates, but if you want to live in extreme climates you sometimes need to go the the upper end of the market, particularly for towables.
I think once you get past the price of a Hitchhiker, you start paying for more than capability, you pay for things that are considered luxury fittings in homes, and you are paying for a custom build to your specifications. These would be in fifth wheels, there are really no super premium travel trailers unless you can persuade Horizons or Excel to build one for you.
A lot of fiver vs TT has to do with size. For many people living in a towable RV, the size that is comfortable, the comfort features wanted, make it too big to be built as a travel trailer. Similarly, people using motorhomes for long term living tend to like them in the 40-45 foot range, which means motor coach or diesel pusher chassis to carry the weight of the house.
Some people, particularly singles with a simple life style, might live full time in a 20-22 foot motorhome weighing not much more than 8000 pounds; not many, but I've met a few. I've met them also towing 13-17 foot TTs behind mid-size SUVs.