I'm interested to know why you can't do stainless. It's stuck around in the market so long because it's very reliable.

As for composite sinks: they will perform like composite counter tops. Anything can be scratched, stained, or damaged with enough rough use. Since it's a granite composite, remember that it won't perform like solid granite (it may to better or worse).

My short answer would be, go with whatever you think looks best. But don't over-pay for something you're not confident in.