The debate between Granite vs Quartz has been on-going for years and depending on who you talk to, one is always better than the other. But it's not as simple as that. As always, it's totally up to you and your needs/wants for the overall look and feel of your kitchen.
So here are the facts:
Granite is 100% natural (minus the sealer). Its quarried out of the earth in large slabs and shipped all around the world from places like India, Brazil and even Canada. Depending on where the granite comes from will determine the look of the slab and no two pieces of granite are the same. As much as we try to pick slabs that look identical to each other it's just not possible....its natural. Often the stone you pick in the showroom, will not be an exact match to the slabs you get in your home because samples could be miles apart in the quarry process. But that is the beauty with natural stones...just like humans, no two are the same and each has a story.
Quartz, on the other hand, is a man-made product. Even though 90-95% of the content is natural quartz aggregate, it's mixed with resin binders to make it strong and practically indestructible. Once it's mixed together, pressed and polished, the finished piece is exactly what the sample looks like...what you see is what you get with quartz. Because of this man-made process, you get a much more uniform look than granite. So if you prefer that look, quartz is a good choice.
The other slight benefit of quartz, it's non-porous and never needs to be sealed like a granite does. Which also means quartz doesn't stain. There are debates over this but trust me, I've seen red wine rings come out of pure white countertops with a bit of elbow grease and a good cleaner. Most granite will require the use of a water-based sealer every few years to keeps its surface smooth but it will never be fully resistant to stains.
Now, most people think because Quartz is man-made it must be cheaper, but that's simply not true. Most quartz products are slightly costlier than your builder grade granite, so it will run you about the same as a premium granite.
So the bottom line really comes down to the overall look and feel of your project. Smooth and natural or sleek and uniform. Well, it's not just as easy as that but it's a start.