I have used both Line-X and Rhino on truck beds. Both are extremely durable. In my applications, the Line-X was about twice as thick as the Rhino, so if thickness is an issue for you, may go with Rhino. That being said I had the products sprayed about 5 years ago so I am not sure how thick they are spraying now-a-days. My friend used the roll on stuff from Auto-Zone. It was a little time consuming to "do it yourself" but was a lot cheaper, thinner and has held up just fine so far. We put it in the bed of his landscape work truck, so it sees a lot of use.
If you are not planning on doing it yourself, I would just contact the local Line-x and Rhino guys and ask how thick they spray. You will be happy with the durability of either one.