I have the spray in liner in the bed, all along the rocker panels and sprayed on my fender flares. Good stuff and easy to doctor up when needed. Dents... are a different story. If your hauling wood and want to minimize the chance of denting the actual floor of the bed, cut to size and lay a thin layer of plywood down after you get the bed sprayed.
Gotta tell you, we put our construction vehicles through hell and back the the the one that holds up the best is the one you don't want, the slippery hard one. I kinda like them because it makes loading and unloading so much easier.
I think it's weird most of you call toppers...caps! I have nothing in my truck bed...besides dents, chips, animal blood etc. I do have a Tonneau cover though!
Anybody who owns a truck and is scared of a few dents and scratches should immediately have their truck confiscated and be given a subaru instead. so there. :D
Personally, the ability to slide things (mulch/stone/etc) is the reason that I like my drop in liner. I like the looks of the spray in but the functionality of the drop in.