I went to an Ed Hamilton symposium a few years back and we got to try a bunch of his products. If I recall, the purpose of the gold is so bartenders could make better looking drinks as the black made them look muddy. The only difference in the formula of the two was the amount of caramel coloring added. We did an exercise where we added like one drop of coloring to water and it made it black as coal. I forget how many "units per whatever" Ed adds to his pot still black to make it what it is, but I'm pretty sure he was saying there was a significant difference in flavor between the two because of the amount of caramel coloring, which is maybe why both products still co-exist? I don't know, I don't think anyone else perceived a difference. At any rate, I've used both and think they're great products in classic drinks cuz they likely represent the style of Jamaican rum that was used in the creation of many of our favorites. Pungent, full flavored, higher proof deliciousness.
FWIW, Coruba used to be a staple in my bar. I find it boring now and hardly ever use it. I think they've continually lessened the amount of pot still distillate in the product to where it's now a shadow of its former self. For that style of dark Jamaican I've lately leaned more on Blackwell or Appleton. But for the most part these days I prefer the funky pot still flavors of Smith & Cross, Doctor Bird, Xaymaca, Hampdens, and things like that.