What do you mean by the same functionality?
If a user is an admin user on the AD, they will inherent those same privileges on Panther when they login; however, if you are wanting to push down preferences and stuff that will hit each user when they login with Panther from AD...you cannot. That's what WorkGroup Manager is for on 10.3 OSXS. You can actually set your XServe to be the AD parent now as well, in which case, you can use WorkGroup Manager to give each user the same functionality...