Andrew:
You probably won't get much useful information here in the replies you will receive. Most will tell you what they bought and how great it is. Few are likely to tell you they bought a cheap or overpriced piece of crap and regret it.
The same common sense rules that apply to other products apply to travel trailers as well. Using a car example a Hyundai or Kia can provide cheap basic transportation but few will argue that these imports compare favorably with a Honda, Toyota, or Mercedes. Resale or trade-in value should also be factored into your deliberation. It affects your cost of ownership as much as initial price.
First, how will you use the trailer? It matters whether you expect a four seasons trailer that can be used in cold weather or just summer camping. How many miles will you tow it annually and how long do you plan to keep it? What kind of roads will you pull it over? Who will use it? An older couple will be easier on it than a young family.
If willing to pay for quality consider the older brand names. If the company is old and still in business it has probably been building good products at reasonable prices. The more expensive ones are probably better . . . quality materials and methods cost money.
Look beyond glitz and glitter. Examine the cabinet and wood trim materials and construction methods. Consider and compare fabrics and materials used. Examine density of foam rubber used in dinette seats and mattress quality. Look under and behind cabinets at plumbing and wiring. Examine a few older used models on dealer lots. The older units that have been traded in will give you a clue how they have held up to towing and use. What is the framing used? Aluminum or wood stick? How thick are the walls and how insulated? Some cheaper units have thin walls and little more than air between the walls.
All RVs use industry standard appliances. Refrigerators, ranges, air conditioners, furnaces, water pumps, converters, etc are made by a handful of manufacturers and are generally the same in all brands. Top of the line units can have fancier refrigerators with more features but all are made by Dometic or Norcold.
More expensive fifth wheels will typically have stronger ie higher-rated axles and springs and use 16" wheels and tires. I've seen lots of nearly new fifth wheels with axles bent so that the wheels cant inward at the top because the axles/springs were underrated for their full load capacity. 15" wheels and tires are marginal for all but the lightest trailers. Read the tire threads to confirm this. A friend of mine bought a brand X fifth wheel several years ago. It had 16" tires but mounted on six lug wheels. Within two years he broke a spring pulling on the interstate highway. When I looked under it I found a pair of 6,000# axles, just enough to carry the rated weight. He bought and installed a pair of 7,000# axles with eight lug wheels and new larger tires.
Decide what your RV budget will allow then consider what fits your budget. Your choices might be limited to lower priced new or higher quality used units. Some will only buy new, some, like me, will buy higher quality used units for a similar amount of money. It is a personal choice. The old adage appliees: You generally get what you pay for.
Harvey