it has a negligible effect in bm games—there isn't a time where it is worse than gold for buying provinces but it is occasionally worse at getting duchies. this generally holds for any time without buys.
bank is pretty bad. i don't think there has been a time where i went for bank where i had to think a lot beforehand; if there is good draw, buys, and you don't have good means to trash treasures then there you go. it's harder when it competes with something like merchant guilds, that's where you weigh exactly how good the draw and actions are. i think merchant guilds beat bank on equivalent draw and actions, although that depends on whether there's a cheap thing to buy a bunch of
one time, opponent and i were going for some good stuff deck with remake and she bought a few banks, and i was like whaaat why would you do that, and then she remade them into provinces, waaah