Qualification - do not have a MP, at least not yet.
The posting you have above is from last August and was an earlier version of Boot Camp prior to it incorporating DMA support for SATA drives. There was a work around for it even at that time though as posted in a how to on Anandtech by slipstreaming the Intel drivers on the XP disc prior to installing and shown in this
link.
This issue has been resolved for sometime, I believe with Boot Camp 1.2 and we're now on 1.3.
The main issue of difference between the MBP and the MP are the FB DIMMs used in the MP. These are designed really for server and workstation installations. They allow for more modules per channel (which allows more memory being installed) but also introduces some latency (vs DDR2, it takes little bit longer to access the memory) into the system.
Most of the tests you will find out there compare the Mac Pro to a box designed for XP. In some things the MP wins out (encoding) and in others the XP box takes it (gaming). The results are primarily due to the different types of memory being used. But in comparing it to your MBP - you should see a pretty significant improvement with the Mac Pro.
For some direct gaming comparisons check
here.
And
here is another bloggers opinion, but he links to the same Bare Feats testing.
