Grit,
I've had bed liners too. I'd still take a spray in vs a drop in. Both can have the bed itself get dented etc. Especially if you drop some 50-100+ lb objects in the bed. Be them rocks, concrete wall blocks, larger logs etc.
Issue I found the liners, is soil, bark, etc can get between the bed and liner, liner moving, the paint grinds away etc between the two.
Reality, which is worst? Not sure. The spray in being reasonably non skid, vs liner very little. Access to ALL the internal bed tie downs etc. The spray is better in the end.
My 02
Marty