Cores, or Processors, you end up with the same difference.
The realistic difference is the Hardware Threads you can run.
HyperThreading for example is counted as 2 Processors by Windows XP, because it claims to have 2 Hardware Threads (when in reality it has 1 with optimisation built-in).
Any Duo or Quad Core System, will show as 2, or 4 Processors.
As for the Core 2 Quad, being a 2x2 processor; that's true, but I have 2x Athlon X4 (which is the AMD variant of the Core 2 Quad) and it shows up as 8 Processors (even in Vista)
The only real difference between these 2x2 and the actual 4 Core processors (due out next year) is you will see increase performance from better caching on most apps .. until they get written for properly with non-mutex apps, because that's where the performance increase really lays with them is in the data exchanging capabilities. Even then they're not that grand an increase in performance.
In any case, anyone who says Vista is crap.. quite frankly hasn't used it. Windows XP Home is crap, it's almost as unstable (or used to be before SP2 not tried it since SP1) as most found Millennium Edition.
Professional has a habbit of slowing down after 2-3months of useage to a crawl. It's why Microsoft just bought out ReadyState for XP that allows you to basically shadowcopy from a state when the system was at a decent speed then you can just go back to it when your system begins to slow and keep what you've already installed.
You know what, after 10months of having Windows Vista installed... no slow down what so ever. Still damn stable despite the fact that drivers have been quite piss poor for it. Oh and there's that whole fact it's more secure too; so many people are bitching about the new UAC stuff and turning it off, but you know what it keeps you safe even if you don't want to install a virus protector.. obviously not from your own stupidity but it is far better in terms of the fact nothing gets installed without an admin say-so who now have far better tools to see when something is being nasty to the system.
Oh and as for performance, the Vista drivers for both ATI and NVIDIA are now on-par DirectX-wise with XP; and OpenGL-wise they're starting to show some improvement over XP (which was the fastest Windows yet for DirectX and OpenGL gaming believe it or not).
Product compatibility has greatly risen but tbh, the fact it dropped has forced developers to actually move into the 21st century and drop the old Windows APIs that Microsoft rewrote for a reason! As for general system performance, Vista is just quicker period now.
