Re: matrox vs s3
I doubt you'll notice much difference in either card but I would test both. That way you'll know which (if either) is the best card. A pretty good simply test is to get online and start scrolling. You can usually measure the quickness of a video card with this very simple test. Another way involves loading a graphic intensive game and test to see which card delivers the best performance. Simply because of S3 struggling to stay afloat, I would bet my money on the Matrox card.
S3 isn't too strong in the support business, nether is Matrox. My personal preference is either ATI or nVidia cards.