Correct me if I'm wrong, but i believe the finest bronze wool you can get is fine grade (#000). This is still less abrasive than super fine grade steel wool (#0000). Best bet: just buy it on WCR and you know it's the right one.
I've been using bronze wool exclusively for a while now, but I'm thinking of switching back to steel for the extra abrasiveness. Also, while bronze won't rust, it does fall apart basically as quickly as steel wool. I would say, test it out for yourself if you have extra cash and are putting in an order anyway and see which you like better.