I've used Samba with Slackware, Suse, Redhat and AIX and there is little or no difference between them regaring Samba.
So it's best to just run it on your favourite OS.
You can setup and manage you Samba by enabling SWAT, or use a 3rd party tool such as Webmin which would allow you to manage the OS and Samba as well.
If you plan to use Windbind and PAM with Samba, make sure your distro supports it.
Slackware for one does not have native PAM support and getting it to work on AIX is rather painful!
"If you always do what you've always done, you will always be where you've always been."