I've had good luck with the rhino liner, Had it on my 97 F150 and on my 05 F150 SuperCrew. Just picked up an 08 F-250 Crew Cab and the Dealer is installing a Rhino liner in it for free for me.
I really don't know much about Line-X I'm sure it's a nice product, But i'm happy with Rhino, it'll take a helluva beating and holds up great, and shit won't slide on it.
GoodLuck though........can't imagine anyone getting a plastic liner anymore w/ spray in's around.