First off, you need to get that carpet out ASAP, that is mold and fungus and can actually make you sick. Yank it out and never look back. If this was a mall crawler Id say go back to carpet, but if your off roading it, go Bed liner, either LIne X, RIno or DIY.
I went the LINE X route.
1) There was one up the road
2) they offer lifetime warranty no matter where you live in the US
3) From what ive seen/heard/read the big difference between RIno and LIne X is that the RIno lining is softer and rubbery, so it is possible in the exteme heats it could get soft and possibly sticky. My LIne X has never gotten that way, but its texture is a bit rougher, esp. on the knees if your climbing around back there.
Before
After
BEfore
after
But here are some points no matter which one you get.
1) Im sure it adds a lil bit of weight, think of it as an advanced undercoating
2) The sound difference between bare floor and Line Xd is minimal. Maybe a db or two. You get use it to, its not overwelming, its just alot diff. than carpet and sound deadening.
3) I love it, its no muss, no fuss, no carpet to worry about and this stuff is pretty durable. Im always sliding hard plastic boxes around. I think one diff. between line x and rino is the added rubber in the rino, so stuff will probably slip less.
A few other points. No matter which way you go, think about future projects/mods that are going to be done to the inside. You can see in my Before pics where I took a sharpie and marked the holes I needed and the ones I wanted filled it. Once they spray that stuff, it is near impossible to find the holes again, its pretty cool For the holes I wanted to keep, I put the factory bolts in there and they just tape it up.