I have Line-X in my TJ. It is awesome, they spray it in very thick. It was very expensive to have done though. I recently rebuilt an old Bantam 1/4 ton trailer, and I sprayed the U-Pol in it myself. I have to say it turned out great.
After I was done with it, I wished I would have done the TJ myself with the U-Pol. I will say this, there is no comparison between the Line-X and the U-Pol. The Line-X blows it away and is more durable. If money isn't a concern, go with it. But for most, the U-Pol diy stuff will work just fine, and will be about $500 cheaper. I just don't think for inside a Jeep the Line-X is worth the cost. If I needed to do the bed of a pickup that was routinely loaded and was beaten on, then I'd say the Line-X is worth it.
"The Wicked Flee When No Man Pursueth, But The Righteous Are Bold As A Lion."