First of all, before you commit too deeply to web portal, read the article I wrote about web portal a while back. There are some
severe limitations to it versus the client software.
Our web portal has only been used by one or two people at a time, so I don't really know how it would perform with 30 users, but the actual performance depends on many things. How up-to-date is your server? How is your network speed? And so on... On an "apples to apples" basis, I would say that the client software performs better than web portal, but that's not surprising, since web portal has the added burden of having to use HTTP.
We use a separate file server because all our file servers are Unix systems. We do this mainly for stability, but the downside is that Windows machines (which the PDMWorks login server has to be) prefer to communicate with Windows, not Unix. We have a great IT group, so they have it working very well, but every now and then Windows decides to stop communicating with Unix. Those situations, though rare, are painfully catastrophic.
(BTW, I'm also an M.E. You can see how far I've gone towards the dark side.)