Well, I'm apparently in the minority here. I had a 2000 Silverado that I put over 220k miles on. It came with a drop in liner and I never had a problem with it. Of course, the rest of the truck rusted away but the bed was fine. For me the drop in liner was best because I liked the slippery aspect of it. I'd fill up the rear with topsoil, mulch, gravel or firewood and it was easy to load/unload, easy to clean out.
My 2016 Colorado had the factory spray in liner. It was definitely tough but to scratchy. It you needed to load something in and slide it into the bed, you were taking a layer of paint or wood off of it. The surface was too scratchy. And a lot harder to clean out after hauling topsoil.
I bought my 2019 Colorado without a spray in liner. Not on purpose, I just found a good deal with all the other features I wanted. I plan on buying a drop in liner but I will take one precaution first. I bought a Herculiner kit and I'm going to paint the bed first. That should protect me from all the rust issues everyone's talking about. Then I'll toss a drop in liner on top of that and the bed should last forever. No concerns about cleaning it out or banging it up with rocks or firewood or whatever.
I do want to make sure whatever liner I get it has provision to access the pockets on the side of the bed so I can mount the D ring tie downs.
Just my view