A3M vs. Ion Auth

I highly recommend Ion Auth. I exlusivly use it for any CI project that require any type of login. For example, I used it on this site https://capitalonemascots.com/ and passed corporation level security check performed by the client. Obviously, this also depends on the rest of your code. (the login is disabled now)

And for those that don't know, the author of Ion Auth is one of the Council members for CI http://www.codeigniter.com/help/about