I bought the Carbon 18 from REI 4 or so years ago and have used it about twice a year, with one of those times being a 16 day road trip each summer so my box has seen prob 20k miles of driving and is holding up very well. Goes on easy, never had any type of issue that wasn't caused by myself. One of the hinges showed some stress on the plastic but I had way overloaded it and just tried to force it closed instead of figuring out what wasn't fitting.
So I ended up getting the Thule Motion 3 XL. We have two big dogs (golden and husky, and the trunk is theirs). I know it’s more expensive than other brands and even other Thule boxes but it looks great on the car in my opinion. Especially if you have a black 4Runner as I do, they are the same finish. I plan to keep it on as we travel a lot on the weekends with both dogs. This one in particular can fit two checked luggage’s and a carry on at the same time while having some space for small items all around. I bought it pretty much right after I got the car. Have put about 10,000 miles on the car with the box on the roof. No issues, easy install, and looks great. For fuel economy wise, when I had the factory OEM sport wheels on the car I lost about 1.5-2.0 miles per the gallon (we do a lot of highway driving). Also a plus is that Thule is have half Friday sale rn so you can get it cheaper than what I got it for . Hope this helps!