Samba & Kerberos
Heimdal or MIT Kerberos?
Samba4 will bundle with Heimdal and Samba4's Authentication Developer works closely with Heimdal's primary maintainer.
From the mailing list:
> The biggest thing users will notice is that the error message system > returns contextual errors, with the actual reason for the failure, not > just the translated code. It often includes the vital clues that help > fix up the inevitable kerberos issues.
Although what this means in real-world usage, I do not know. The general consensus I have found seems to be that one is just as good as the other, and you should just use what your linux distro has by default.