[Samba] what's good for security=ads ?

[d tbsky]

hi:
   we have a 2003 R2 domain. it is running on 2003 native mode. we
want to setup some samba member file servers. our client is windows
xp.

   i try samba 3.2 with "security = domain" and "idmap backend = rid".
it seems fine. but i saw there are more advanced options in samba like
"security = ads" and even parameter about "rfc2307"  to mix windows
and samba. they are complex settings and i wonder what benefits they
bring to us.

    our situation is:  we want to use samba as file server for windows
xp,and we have one single 2003 R2 domain. we may want to migrate to
samba 4.0 when it is ready.

    is simple "security = domain" enough?, or we should setup
"security = ads" to prepare for the future?

    thanks a lot for your help!!