I bought a new tundra back in 05 and had a rhino liner sprayed in the bed. Pricy, yes, but one of the best add on purchases I ever made on a vehicle. I still have the truck, I've hauled stone, concrete blocks, X# of cords of fire wood, cow manure, you name it, still as good as new. It hasn't even cracked around any of the dents. Would spend the money again, and never look back.
I have a Rubber Queen mat that I bought 25 years ago and has been in 5 trucks. That thing is the toughest piece of rubber I have ever seen, and I doubt they even make them to those specs. these days. I truly think it will be around for another 25 years, I doubt if I will !
I've seen the drop in liners cause problems, I'd go with the spray on.
I've seen a big difference in different spray in liners, so do your research. Rhino is the best as far as I'm concerned, IMO. I had to have the tail gate of my tundra replaced 7or8 years ago, the body shop used their spray on liner, it didn't last 6 months. Took it to Rhino and they redid it. Still going strong.
One week after I bought my '03 Silverado, I got a place in Honey Brook , PA. to put in the spray in liner(I don't think the place is there anymore). It was pricey, as they stripped off the paint, then applied the spray in liner. 15 years and 300K miles later, there is one 2" spot on the wheel well that the liner has come off(probably because they didn't get the paint all the way off). Other than that, it's still perfect.
I agree with bad primer on the brine solution, I'm even blaming it on all the small holes in my garage concrete floor.
Now this is just my opinion, I know of no study that confirms it. When I was doing PA inspections on vehicles I noticed that vehicles that got driven very little or only short trips the undercarriage would be covered in rust. My theory is that not being driven in the rain much it was never washed off, and didn't get the fine mist of oil covering that comes when it rains, off the wet road.