Most drum libraries fall into one of two categories: do-it-yourself or ready-to-wear. Superior Drummer is in the former, BFD the latter. Neither category is better at all things. Superior can give you exactly the sound you're after, but it'll make you work for it. BFD takes less effort, but unless you have the budget for lots of expansions you may sometimes find yourself settling for "close enough".
As a longtime Superior Drummer user, I have learned how to get good results with it. However, it's still a bit of a PIA due to its philosophy of modeling real-world drum mixing. I don't have any additional kits for it because they're pricey, so if I need an alternate snare, for example, I turn to Kontakt libraries. (There are many inexpensive drum samples out there, both full kits and individual drums from the likes of
Drumwerks for 4 to 20 dollars). Many users would find my approach archaic, klunky and obtuse, especially if they have no experience mixing real drums. It works for me, though.
But if I was looking to add a Category 2 turnkey drum library, I'd seriously consider
Steven Slate Drums. Although not as tweakable as Superior, it's one of the
easiest libraries to quickly and effortlessly get good results with. Plus at $149 it's a steal - less than the price of one Superior Drummer expansion - and you get 100 kits.