Is it the Ultra Liner dealer telling you that it's the same as LineX? That to me is suspicious... At any rate, I've never seen a truck with it so I don't know but what I do know is if the guy is priced right and you like the looks of it and can see one that's been used a couple of years (that he did), then it's good stuff if it held up. I know what I'd do (get LineX) but that's because I've put mine through 3 years of pretty hard work and it looks as good as new except for (very) slight fading.
As a side note, as was said by Wrecker, it's primarily in the prep and the guy that did mine moved in next to my son just a few weeks ago. He remembers my truck and said that if he had let one of the workers he's had since then prep it, it wouldn't still be looking so good.