Both are very good. Quartz is very low maintenance, granite needs to be sealed occasionally. Sometimes the seams in quartz are less noticeable because the material is more uniform. Granite, being a natural stone has variations that can make seams more noticeable. Both cost similar, but some quartz can be more expensive.

It also depends upon the exact granite that you're thinking of, some are virtually indestructible others have issues.

There are tradeoffs for each. Do a little research independent of your stone salesman.