Don't want to complicate matters but if you can get your hands on a gold hardware with caviar - they hold a special spot for me. For black, I like the boy lambskin or calfskin with ruthenium but prefer gold with caviar.
Hmmm I see classic flaps that are more dressed up/elegant going better with gold, whereas personally I like my boy bags cool and edgy which means I prefer ruthenium, black, rainbow and silver hardware for my boys. However, that is entirely a personal preference thing of course. There are plenty of ladies who like to wear boys in a dressed up way.
I think the feel of the boy is around the edgy / casual looking which suits the ruthenium hardware better. I personally prefer owning a boy in ruthenium hardware (young/casual look) in combination with a classic flap in lamskin in ghw (luxurious / classic look) - this combo provides options for any occasions!
What color of jewelry do you wear most often? Do you want hw variety in your black chanels? Do you wear your bags crossbody or on the shoulder more? My worst buyer's remorse is getting something that looks gorgeous on others, but I hardly ever wear For me, it's gold hw, the shinier the worse. LOL