I was told they are the same directly from Durabak.. I was in a pinch because I was spraying my 55 and got some bad advice about sprayer pressure so it was glopping up and too thick in some places so I had to buy a few more quarts when a gallon probably should have done the trick according to their estimates. Being 1/2 way through and not having to wait for shipping the guy felt bad for me and I finished with a couple extra quarts of herculiner and he was correct, there was no difference what so ever.. It looked great especially when first sprayed.. I also did *very* extensive prep work, but I expected it to be like "bedliner" in that it would hold up.. Unless you use at least 2 gallons, its very thin so that is a weaknes.. As soon as you put axles, loose metal objects, or even just dialy wear and tear, it will probably tear.. Even in high wear places such as under your feet it tore for me.. So that is my $.02 on it.. I would not do it again, I would spend $400 or so and have someone do it with the thicker rubberized stuff that is more durable... Just my $.02 on it...
Also I was at an autobody supply and they sell a kit for about $150 that is a "finally, a spray it yourself bedliner" that seems more like the real deal.. You have to wear a respirator and it at least seems more heavy duty.. You can proably find a review from somone out there on the net who's used it.. You need the "right gun" I remember from the literature but my guess is it probably the same $8 "Rock schutz" gun I used to spray my durabak...
If you search I have a photo somewhere of how it looked and how it didn't hold up...