Anything black is likely to get scratched and appear less than black eventually. A sink gets a lot of abuse. As long as you don't get a polished SS sink (which since it will get scratched, now looks funky with the other areas nice and shiney), it will be better long-term. In the short-term, the composite sink will probably be quieter, especially if you have a disposal attached (but the better ones of those are pretty quiet now, regardless). I do not know if you can repolish the composite sink. You may find that is an acceptable way to extend the time it looks good. no idea if it can be done, or how successful, or how easy it is.