I am an interior designer, and I do not recommend granite. It is very popular, but it is not the best product for the money. I recommend engineered quartz which is sold by the brand names Silestone, Wilsonart, Zodiac, etc. If you find a good installer and supplier, no one will be able to tell the difference between engineered quartz and granite.
Granite can scratch (and when it does, it allows for microorganisms to grow), it can stain, and it can burn. Engineered quartz does none of these. I know that many people do not seal their granite countertops, but if they don't, then liquids will soak in to the granite and stain it, and it will scratch. Granite costs more than engineered quartz, and engineered quartz is a better product.
Corian is cheaper than either of the other two options. It doesn't need sealing, and it only needs sanded down every few years to renew it. It doesn't have a glossy shine like granite or engineered quartz. People either love the look of Corian or they hate it. If you are ever going to resell your house, I'd go with the engineered quartz or granite.
So, here is the same advice I give my clients. Engineered quartz is the best product for the money.
L.