Authlogic with nifty_authentication, why use both?

Authlogic seems to be defacto now for authentication, but I was
wondering how it compares to nifty_authentication.

The nifty_authentication generator does make it easy to use it along
with Authlogic (configure the gem, then script/generate
nifty_authentication -authlogic, I believe), but I was wondering why
one would want to use both. Nifty_authentication states, "This is
similar to restful_authentication, but simpler." Well, isn't that
goal of Authlogic as well? I'm sure they're two solutions to the same
problem, but just wondered why I'd want to use Authlogic as well.

Nifty_authentication does generate a lot of the validations as well,
so I see it's benefit, but why use Authlogic as well?

Nifty_authentication is a generator to generate the files needed to
use authlogic in a rails app. Not to be confused with what the gem
does. It takes the place of building the User, session and adds some
helper methods. Run script/generate nifty_authentication --help to see
what it does.