I originally used categorically to mean "unambiguously explicit and direct", but adding to what you said (with which I mostly agree), Scrypt actually does provi

I originally used categorically to mean "unambiguously explicit and direct", but adding to what you said (with which I mostly agree), Scrypt actually does provide a categorical increment to security by being ASIC-resilient. There are differences among them between classes of attacks they're susceptible to, provable security properties, and how paranoid should you should be in respect to advances cryptanalysis. I tend to weigh these as significant factors given that the dynamics of password-based auth can very well lead to a database leak screwing someone over 20 years into the future, although I admit that you can't get too picky nowadays and I'd be very glad if we, as a species, could have what you described as a lower-bound (with the exception of PBKDF2, of course :P)