Man-made or Au Naturale? Quartz v.s. Granite
There is no black or white answer to this question, but I do promise an unbiased approach (side note: I am a fan of both). With any selection of material type, finish, colors we need to know what our priorities are. Is it maintenance? consistency? price? location? It's no different when trying to decide between granite or quartz for your countertop.
Lets start with maintenance.
Quartz

Some customers who walk through our doors who come in right off the bat looking for quartz, when questioned, " Why do you want quartz?" will usually respond in this fashion..."I heard its practically indestructible, maintenance free, and comes with a lifetime warranty." This is the part where I remove their rose-colored glasses... gently.
1. No material is indestructable. I mean look at what happened to the Titanic. But, unlike the Titanic, no quartz brand has marketed their product as bullet-proof. Here are the three claims that Caesarstone makes.
a) quartz is highly scratch resistant
b) quartz is resistant to most stains
c) quartz is heat resistant
The important thing to note is the use of the word resistance. Resistance does not have the same meaning as using the word "proof". Meaning that it is possible to scratch, stain, and scorch quartz.
Caesarstone even recommends to not cut directly on the counter and to use a trivet for hot pots and pans. Quartz is not recommended for outdoor use and is not recommended for flooring.
The chances of the counter scratching or staining is decreased and most people have not had a problem with the proper care. But, I have seen some pretty bad scratched up quartz from careless plumbers or other workers. And I have seen some pretty bad burn marks from a hot pot placed directly on top of the counter for hours.
One has to remember that quartz is also made up of resin, i.e plastic, thats how the quartz particles are bonded together. Chips are also pretty common ground with quartz. I have only seen stains with white and other light quartz colors, but most stains come out with Soft Scrub with Bleach.
The moral of the story is we have to take care of any investment.
2. Maintenance free. If by maintenance you mean no sealer, than that is correct. Not because of the quartz content, but because of the resin content. But Caesarstone does advise that their honed and motivo finishes do require more maintenance. These finishes can scuff and yes even stain.
3. The Lifetime Warranty. Brands like Caesarstone do have some form of Warranty, some are lifetime and others are 15 or 10 year warranties. So there is some protection on your investment but its very limited and you must follow their Care & Maintenance requirements to be covered. Common damages like chips and scratches are not covered under the warranty.
Quartz is a great product but other than the Lifetime Warranty and sealing, there is not much of a difference between quartz and granite.
Granite

Granite is highly scratch resistant, stain resistant, and heat resistant. We have never had customers needing scratch or stain repairs on granite. Granite can chip, usually in the sink area or edge but it is easily repaired and goes unnoticed. This is where granite has the upperhand on quartz. Repairs on quartz, like chips, are more noticeable and nothing can really be done about fine scratches because the factory polish cannot be matched. Stains that cannot be removed with Soft Scrub with Bleach are permanent.
We recommend not cutting directly on granite but not because of the likelihood of it scratching but because granite is harder than the the steel blade. Hence, the granite will dull kitchen knives.
Yes, most granites should be sealed. But, it is such an easy application that should be done once a year, or every 15 years depending on what sealer is used. If water beads up on your granite you are good to go, if it doesn't, its time to seal.
Cost
Unless you are going with Caesarstone A grade or Cambria, quartz has the same price range as granite. Caesarstone has 2 grades of material A being no imperfections and B having a dime-sized imperfection or blotch. Be weary of buying Caesarstone that's too inexpensively priced to be true.
There are a few colors of granite that are cheaper than the lowest priced quartz. What can change up the price range is the number of slabs that are needed to complete the project. Quartz slabs are small in comparison to granite slabs. For example a kitchen countertop that requires two granite slabs, depending on the layout, may need three or even four slabs of quartz to minimize the amount of seams.
Consistency
Quartz gets the upper hand and wins in the consistency department but that only matters if you are looking for a solid color with no movement. For the most part. Slabs of quartz can have a dime sized blotch that looks different than the rest of the slab. Here at Luxus we are good about screening these out.
There are a number of consistent granite especially in the black and grays. But there is no solid white option like you can find in quartz.
Quartz has a smooth surface there are no pits or fissures like in granite. But pits fissures, and variations are what give granite its character, charm and beauty. Quartz's lack of variation is what makes it appealing to some, while variation is what makes natural stone appealing to others.

Consistency starts getting into the heart of the matter, which is the asthetics. Both products hold up very well and once its installed, there isn't a real difference as far as daily maintenance is concerned.
Those who love veining and movement go with granite. Although, certain quartz colors try to mimic veins and movement of granite...it still looks man-made and doesn't have quite the same depth of natural stone. Don't get me wrong there is nothing wrong with that, just, you are not going to fool anyone into believing its granite. Its quartz and that's what it should look like. Although there are a few brands of quartz that can mimic marble very well.
It makes more sense to go with the asthetics, what's the look you are going for?
Do you like the look of granite or the look of quartz? That's the real question. There are certain styles that can only be achieved with quartz, other times with granite. Either case, both products make excellent and durable countertops.