My experience with bed liners:
Rubber mat - Keeps floor of bed in good shape and keeps items from sliding around when loaded but does not protect the wheel wells or bed walls from damage.
Drop in plastic liner - Keeps floor, wheel wells and bedside in good shape but very slick when carry loads and abrades paint when flexing under load.
Spray on liner - Protects entire bed from scratches and abrasions while resisting loads from sliding but does not protect against dents or punctures.
After having these three different liners, I would suggest a spray in liner for scratches with a rubber bed mat for dents.