Emilio, take a look at the Rust Bullet products as well - I used it on my inside floor pans just recently, you just brush it on (one step process, POR 15 is a 2 step process). Turned out real nice ... I still have a few extra 4 oz. cans if you want to try it (it only takes 2 or 3 to do the insides).
FYI, there are a ton of commentaries/reviews/critiques out there for all of the options you are looking at ... everyone has their personally favorites.
Craig