Linux is a kernel, for one. Distributions only provide updated packages or glue apps to pull together the initial installation.
A better question would be:
What Window Manager and/or Desktop do you use?
I have yet to see a device driver not work across any particular kernel version, ie. what Linux really is. The distro is just a box with wrapping paper and a url to grab updates, which they got from the original author in source form.
I currently use 2.6.11-13smp, which I built from source. The original install was Mandrake 2005le (alumni from 7.2 days) but the only things really left is their Perl admin stuff (very nice). On top of that, I run KDE 3.2 with all the candy turned on.
As for performance and why graphics cards run better on a Windows install is purely business. Vendors like Microsoft buddy up with the device peeps in the market to make their shite smell better...and it _usually_ does. I get better fps in Quake3 running Linux 2.6 than I did with my _very_ trusty W2K (odd?). That is, of course using nVidia's closed source drivers...which probably have undisclosed M$ code in there somewhere.