J15

Depending on what you do with your truck, the highest numbers aren't always the best. The "harder" liner may be more prone to cracking instead of flexing to avoid failure. In the end, both liners work well and it's a matter of personal needs.

Martian

Exactly this. Example: Glass is VERY hard. But hit it with a hammer and see how it deals with it.

Stage4

Good point, but stronger doesn't necessarily mean harder. The TDS's also show durometer (hardness) and elongation, so you can compare.

The LINE-X lifetime warranty covers "cracking, bubbling, and flaking" and I think that most major bedliner companies offer that.

EDIT: Hardness Info. The higher the number, the harder the material. Range is 0 to 100.
LINE-X XS-100 - Shore D 50 (tear strength 490 psi)
Rhino Hardline - Shore D 55 (tear strength 250 psi)
Rhino Tuff Grip - Shore A 88 (google search a conversion, A88 is about equal to D43) (tear strength 250 psi)

TheMenchess

I had a plastic liner that I took out to find the box had some holes in it. Mostly because of the climate here in Canada and what they use to salt the road with. I took it out, took. The box bolts out, welded pieces to fill the holes and then after sanding it I bought "shake and shoot" at the Bensons auto parts store. Applied primer first then it took the entire kit to spray in the bedliner but it looks amazing and it's so far really durable. Looks like the expensive liners, but cost me under $150 and I did it myself.