Jimbo,
I bought a bass-boat-red fiberglass tank on Ebay for next to nothing for a spare. I lined the inside with the Bill Hirsch stuff but have yet to put any gasoline in the tank. Therefore, I can't give you an accurate account of how well the coating holds up in service.
There are some noticeable differences, however, between Kreem and Hirsch. The Kreem product seems more rubbery than Hirsch. The Hirsch dries to a smooth, shiny finish that is supposed to adhere better to fiberglass than Kreem.
Jason