How long is a piece of string??? that is what you are asking.
You give no info as to what either of these GPUs will be attached.
I would not put either card inside a box with less than a CPU with
2.8Ghz or equivalent, 1024Mb memory and at least 80GB HHD.
What chipset does your Mobo have.
Do the cards have 128 or 256mb - 128 I dont think will be much good in
vista - but dont know - ask there in vista group.
I have not read up on these things.
I think the ati is out as far as vista is concerned. Not sure re the
6600 but I am certain the 6800gt. But there are not as yet, as far
as I know, drivers from ati or nvidia for either card being used with
vista. If there are then they will be test ones, beta, so could be very
unreliable, like most beta stuff.
You would need to check their sites, register and ask in there.
Asking such a question in windows.general will not generate much
feedback - if it does I will be surprised. I would perhaps have
chosen a group more suited to the usage, like games, or even the
vista groups. But -
Try a Google for comparison tests - I did when I was deciding bet Ati
and nVidia - I wanted to improve on the 9800Pro which in my humble
opinion, with P4 478 pin CPU, was a great combination for my usage.
But it depends on the usage - gaming or writing
letters/media/photography/simulators.
Do the research in the various forums and tech sites for the field in
which you are interested.
This is the sort of site I mean
http://www.a1-electronics.net/Graphics_Cards/GeForce/2004/GeForce_6600-GT_Nov.shtml
Most tests etc are done with games - sets the standard for picture,
colour and frame rates.
nVidia have had a good edge on ati for some time now and have only
just very recently caught up. But the current models from both sides
are very expensive. The Ati 9800's, in my opinion was the last time
ati had the edge over nVidia - but they didn't hold it for long
If you can stretch to a 6800gt even better.
Good hunting
Antioch