Active Directory Membership vs. SQL Membership

Greetings,

My employer is planning to implement a full re-write of our website (currently mix of Oracle, PSP and PHP) TO ASP.Net. During the specs layout I wrote a document on Login procedures. My recomendation was to use SQL Membership provider for our customers (1 million +). However, our SA is pushing for using Active Directory Membership Provider.

I was under the impression that AD is a good choice for non-outsiders like internal employees etc. and i think using AD for so many regular site users will be a mess versus the way we can manage user logins in SQL DB.

I maybe wrong in my conclusion, hence posting my question here. What are your thoughts on this? Do you think AD as regular site authentication is a good choice? especially if you can throw some pros and cons, i will be very very happy.

 Thanks in advance for reading this and taking time to write something!
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