I don't know if there is any place or information that gives a rating value for different campers/manufacturers. Pretty much, all of them are made the same. Some use aluminum construction, others use wood. There's only a couple frame manufactures out there, and almost all the appliances come from the same place. There might be some manufacturers that offer a bit of personal customization, but you're going to pay the price too!
Higher priced does not necessarily mean better quality. Almost all manufacturers have three tiers of campers, a light weight-beginners-entry level, a mid-range little more expensive with extra features like outside kitchen arrangements. Then there's the higher end that adds bells and whistles, and usually longer and heavier ... more like the Toy Hauler idea .. made to be more rugged. There again, the price goes higher with each tier.
The thing you need to do first is to identify the type of camping you want to do. Boondocking, full hook-up State Park camping, Nascar circuit, Full timing, 2 week summer vacation only.
Next, who will be camping with you? Wife and husband only, Kids? how many, how old, and any other guests.
Then you need to target the kind of camper that meets your needs and wants, and then begin comparing across brands and manufacturers.
You may find than a reasonably priced "entry level" may fit the bill perfect.
It's important to make these decisions early, because if you plan on purchasing a camper that is designed for light weight use, and you end up taking it mountain climbing, you'll destroy the camper quickly. So basically, every camper is good, and every camper can be bad. It's really a matter of what you plan to use them for. An kitchen chair may be rated to support 150 pounds. If a 600 pound person sit on it, you can't blame the manufacture when the chair breaks under the load. It was designed for 150 pounds and it broke because the chair was misused. The same is true of a camper!
Most campers, under reasonable care, will provided years and years of trouble free service. There's always exceptions, but those are the exceptions.
So basically, I'm saying, they are all about equal. Look for the floor plan that fits your needs and then narrow down the price you can afford.
It really helps if you actually GO and visit dealerships and compare camper to camper.
Good luck!
