Fax Server or workstation server

Hi,
I’m going to create a fax server with specfic software to run on it. The software for the fax server does not have to run on a server(as the o.s), it could run on a windows 2000 professional as the o.s. Is there any reason I should install server as the o.s. or would 2000 prof. be sufficient? Just looking for opinions..
Any help would be appreciated…