There is a company I work with regularly that puts out a flyer about the 20 most common kitchen countertop mistakes.
http://www.precisioncountertops.com/i/pdf/kitchen.jpg
It may help you with some of your decisions.
I tend to like the composite engineered stone materials such as quarts. It is uniform, in appearance and there is only a small variation in color from one lot to another. You never have to seal it. I think the seams can look better than granite. Quartz usually comes with a warrantee around 10 years from the manufacturer.
You can place items directly from your oven or stove top on granite without worrying. Granite is a natural stone with flaws and imperfections fissures and cracks that add to the look of the materials. It is a unique product and every slab is different. Most granite will require regular maintenance to seal the stone. Sensa granite is a pre sealed stone that requires less maintenance.
There are many other good surfaces besides these two. I would recommend visiting a home center and speaking with a salesman about the differences. Remember that if you talk to a shop that only sells one product they will be biased toward their own.