File server OS in Mac/Windows envrioment?

I have a ad agency client with an old xserve for a file server. They have 13 Mac users for creative work (Quark, CS4, etc) and 20 PC users doing account/administrative work. They also have a in-house Exchange server for email. They have 2 logins currently, one for file server and one for email. It is time for a new file server and the big question is Windows or Mac for the file server. In the past my experience with hosting macs on a windows server was awful. We needed 3rd party software to make it work. But that was in the NT4 days. I have not tried it since. Goals Single logon (AD or OD/AD) Mac and Windows users accessing same file shares. I am comfortable using either server software. Mac file server Pros; 1. I have used it before and it works. (without AD) Cons; 1. No xserve -> no redundant power supply 2. OS X server AD integration Windows file server Pros; 1. Single server OS 2. Proper server hardware Cons; 1. Macs connecting via SMB I think it comes down to what is the bigger headache, getting Mac clients to work with a Windows server or getting the Apple server to work with AD. Thoughts? Thanks