I have nothing against SiS, for the money, the chipsets are ok. But you could do better in terms of reliability, performance, etc. by going with VIA.
At least the KM133 uses a few tried and tested ideas. No matter how much people complain about the S3 Savage4 line-up of cards, they did a decent job and even though the technology is heading towards 2 years old, it still is better than what SiS can offer.
I also have more faith in VIA's other motherboard components such as the IDE controller, etc.
Let me put it like this. How many updates have the VIA 4in1 drivers seen lately? Quite a few in the last few months alone.