The stuff I used on my trailer was the LINER X-TREEME, recommended to me by Nick (nicks trix) and found on Ebay. The seller is a great guy, and the product has held up great. The trailer has made a couple of trips to Baja, and hauled the racer around for a couple of years now and it still looks like it did when I sprayed it on. I honestly couldn't be more pleased.
here's the original thread from 2 yrs ago..
http://classicbroncos.com/forums/showthread.php?t=88005&highlight=trailer+bedliner
let me chime in on what scott said. i came a cross the product on xtreem ebay and figured for the price i'll try it.
once it came i tried some test panels. the way you are to put the ground up rubber bits in it i felt it was too gritty & was too runny for under the truck for me. i thought it would be fine for a trailer rather than a bronco. i am not a fan of the skin shredder liners like many of the DIY are. i prefer a smoother texture. that's just my taste. i wanted something that didn't hurt you & would wash easily. i've seen scotts trailer and it looks great.perfect for that application, he & his boys did a great job on it.
i just had my body shop redo my car hauler and they used Upol on it. it's got a nice look & texture. we just hauled a big heavy peice of euquiptment on a pallet and it did wear through in a rub spot (pallet against a side). i have extra liner left over that i think i'll touch up with. i'm pleased with that product for it's purpose.
for the bronco i am sold on the SEM. it's 2x the price of Upol but i love the results of it.
i think it comes down to what texture, look & what you can afford.
i think the key though is really in the surface prep for a big part of the durability.
for those that have a rhino liner that has fadded, i found a product from my local linex dealer that is a UV dye that works great. rub it on and it recolors the material. it's about 45 a pt. that will do a whole interior easily.