I run both sides of the coin here at work, and I much prefer the function in UNIX vs. Windoze, but I am biased to UNIX from working on it longer. I do not notice any major performance issues speed wise, but I hardly ever get the "Click OK to Terminate" like on the PC. There are times when functions that bomb the PC work like a charm on UNIX. Could be a memory issue, not sure since I get no warning, V5 just bombs out requiring a full cold restart. Ford requires UNIX, since they refuse to support PC based TeamCenter and V5 together, even though both will run on PC, and I have seen them run both on PC laptops in update training sessions. Go figure....
One other thing that bothers me about the PC side is how we maintain our drawings for EC releases. We want to keep all old release levels in one document so here's what happens: I copy/paste the entire page in UNIX, and all dimensions, GD&T and notes are there in the copied page views. If I open the same drawing file on the PC and do the exact same thing, half or better of the dimensions will be lost in multiple views. I am not sure if it has something to do with the Ford-specific system settings of V5 on UNIX or just one of those things, but it is a major time waster on the PC to have to interrogate view to view to make sure all the stuff is there. So for now, I copy pages on the UNIX box to preserve everything, then just run the update view function on the PC. Copying views to a new page in UNIX is no help either, gives me the same problem as seen on the PC.