In case anyone is interested here is the Windows XP vs. Vista: The Benchmark Rundown from Tom's Hardware.
It concludes:
Windows Vista clearly is not a great new performer when it comes to executing single applications at maximum speed. ...
Overall, applications performed as expected, or executed slightly slower than under Windows XP. ...
There are some programs that showed deeply disappointing performance. ...
We are disappointed that CPU-intensive applications such as video transcoding with XviD (DVD to XviD MPEG4) or the MainConcept H.264 Encoder performed 18% to nearly 24% slower in our standard benchmark scenarios. ...
With such a fine operating system as Mac OS I don't see why anyone would install Vista. I only use XP because I *have* to use Outlook, Excel and Powerpoint for my work. When the UB version of Office comes out next year I hope to go pure Mac OS. And I really wish there was good webcam support for Windows Messenger Live in Adium then its adios XP.
I don't see any value in AreoGlass since Mac OS already has graphics that are far superior.
And Mac OS - I understand well because its UNIX. XP has sooo many side hooks and funky intergrations that it makes the whole system unstable, and concurrency is such a problem it blocks for no good reason. Reading the report, I am not sure Vista has any significant kernel improvements over XP that benefit real world uses.
My humble opinion.
BTW. Parallels is the best investment I have made for my Mac! Thanks guys.