I can't say anything about U-Pol bedliners. Indeed, I have never heard of them!
My previous truck was a 2003 Chevy S-10 ZR2. I had a LineX spray liner put on just a few days after buying the truck. It still had less than 100 miles at the time. In ten years and 186,000 miles the liner worked VERY well. I would do a LineX again in a New York minute.
My Nissan came from the factory with a spray liner. After four years and 63,000 miles it is working well. No problems with it at all.