I *thought* that I remembered a post where Mirza said the bronze ones were heavier but I may be losing my mind. I can't find an official GM source anywhere confirming that the bronze are forged - but
@Mirza Grebovic said so in
this post.
I had wheels drop shipped to the shop, so I never got to weigh them without tires. The bronze set with PS4S are a couple pounds lighter than the polished with Cooper all-seasons, though I think that's to be expected given the tires.
Finally, the wheels are inscribed DICASTAL - which for a time I thought meant they were cast, but I have since realized that's the name of a company making wheels for GM.