I've shot both and they do share a fairly thumpy feel with the Gamebore perhaps a tad harsher, they're both excellent at breaking clays but too dear compared to many other shells out there that do the job equally well at up to £50 less per thousand. The Black Golds look more upmarket and are possibly the easier shell to get hold of on a regular basis.
Yep, I shoot hull sovereigns all the time, last year at the worlds in the US I managed to hold of some black golds. In two weeks I shot nearly 2000 of them and can honestly say there's nothing in it. I'd go with the one you can get hold of easiest and cheapest
I shot the sovereign parcours with a mix of eley superbs for the slower closer stuff last weekend happy with both it was nice to have that extra option on faster clays