Mike,
I don't know anything about Herculiner, but the idea of a "do it yourself" project that would have this much of an effect on the appearance of the truck would be daunting for me. If you are not happy with the end result, you have no recourse except to strap on the self-administered butt-kicking apparatus and start pulling the rope...
"Linex" was the best available option for me. I had "Rhino" sprayed on my first truck and was generally pleased, but found that it would get soft in our extremely hot, sunny Atlanta summers. Occasionally I use the bed of the truck for hauling gravel, or loose pine bark and, when shoveling out the contents, the shovel point would tear into the soft Rhino coating and do some damage.
Linex is much tougher stuff. They seem to have perfected the substance that they spray so that you can count on a uniform thickness, a slightly tacky "grip" (particularly when new), and a very durable surface that won't tear from impact damage (shovels, whatever).
Our local Linex franchisee warranties the product for the life of the truck. I had one, small, damaged area and they repaired it, no charge, two years after the fact.
My truck was sprayed over the rails. I think the cost (long bed) was about $400. 00. They will color match your factory paint, too, but I just went with their standard black.
If you spray in your own liner, be sure you are familiar with the process and that you have masked all the areas really carefully, too. The guys that did the Linex were really artists --- the liner looks like it's always been there and looks like a stock part of the truck. Makes a hugely positive visual impression!
I have a diamond point toolbox that is very heavy; it is clamped to the top of the rails and has been on and off the truck maybe a dozen times. After two years, there is no evidence of the wear and tear to the top rails at all. The Linex is an amazing product.
If you are in south Florida, you are in the harshest environment in the country (more UV "hours," salt corosion, etc. ). I'd want the best protection my money could buy, and I'd want somebody else standing behind it if there were ever a problem...
Best of luck.