Quote from Toonces:
Is there a clear winner between these platforms? There were some discussions a while back, but it's been a few years, so I wonder if anything has changed.
I remember that Baron had something on this site a while back showing that 2000 was the best platform, but I believe that was before the release of XP.
There is very little difference under the covers: as others have said, turning off unnecessary services and driver loading results in a very slight performance improvement in the XP/2003 series versus the 2000 series.
That said, our decision was to completly bypass the XP/2003 - actually start a very expedited migration off of $soft servers and clients - to Linux on both our servers (a no brainer) and also our clients (somewhat controversial by in the end justified by metrics and thus a success.)
If your platform etc allows you should take a hard look at open source solutions. If not then the xp/2003 stuff works well with adequate resource utilization when properly configured.