Well we will just have to wait and see lol everything points to haki being the answer for me agree to disagree until more info comes i guess. To me at least Everything in the story points to haki being the trump card in fights not dfs.
Personally no i wouldn't agree there, mihawk told zoro if his swords (which was no named) were infused with haki they would not have broken mind you these swords clashed with yoru the strongest weapon so if there hakis are the same It would stalemate for me.
Example 1: oda has established that the one with the greater haki wins.
replace zoro for (black blade yoru shanks) if his haki is not greater than pica replaced by (Bamboo blade shank) then they stalemate zoro(black blade yoru shanks) would need to surpass pica( bamboo blade shanks) haki in order to win.
As i believe the true benefit to a black blade is making one yourself if it was shanks with his own created black blade vs bamboo shanks, black blade shanks wins as him creating his own black blade makes him stronger and his haki grew stronger as a result.