So many different kinds of composite sinks out there, you can't just make a blanket statement like that. If the local appliance store wasn't more specific than what you've written, find a store more knowledgeable. Why are you shopping for a sink at an appliance store?

If you are looking for a composite sink, I suggest you check out Blanco Silgranit sinks. They don't scratch, and any cracking that is possible would happen in transit by poor suppliers who don't pack it well. If you buy from a reputable website, like qualitybath for example (I have no affiliation with them), the Silgranit sink will be packed well, and arrive undamaged. Once installed, it will not crack.

Why is the word "faucet" in your subject title?

I'm not very good on the computer and I'm trying to change faucet to composite and I can't seem to do it. Thanks for your comment. That's exactly right. The sales lady said when they come in from the manufacture seems like they have cracked. I checked with consumet report and they don't like it.