First, the similarities. They are both stone, which makes them hard, heavy, expensive and time consuming to install. They are both natural products, which means there can be variations in color and pattern, and sometimes what you see in the display is not very close to what you actually get delivered. Both come in a wide range of colors and patterns. Both can be stained by oily or highly colored foods. So both require resealing every once in a while (it seems like yearly is the usual rule.) Both are relatively heatproof, and they won't scorch (a very hot pot placed on either type of stone could crack it, theoretically.) They start at about $60 per square foot installed, but granite can go as high as $200 per square foot. But granite is a much harder, stronger stone than marble. It resists impacts and scratches better. And it is resistant to acids like tomato juice, lemon juice or vinegar. Marble is simply calcium carbonate, just like chalk, but in a compressed and crystallized form. So acids can etch the surface permanently. (And it will fizz, just like chalk in vinegar.) And it cracks and scratches more easily. Some marbles have very little pattern (some are totally pure white) so stains and marring stand out more. Granite typically has a complex mottled pattern that hides stains better. So for hard use, granite is a better choice. A marble countertop or slab is a traditional working surface for pastry chefs, because the cold stone keeps the butter in the pastry layers from melting. But polished granite would probably work as well. Practical considerations aside, marble has a look that is possibly more elegant and luxurious. It has extremely fine crystals, which create a snowy or satiny look. And the colors and patterns can be quite dramatic. Granite tends to have larger crystals, perhaps the size of peas or rice grains. This creates a coarser, more sparkly look. And while granite comes in a range of colors and patterns, that range is probably narrower than for marble. So most people seem to recommend granite for hard use areas like countertops. Marble is higher maintenance, less durable and about as expensive. Its one advantage may be in appearance, but that will depend on the owner's taste and the kitchen's overall style. But just FYI, there is another possibility that is even more durable than granite, and that is quartz or "engineered stone". It is made of quartz powder that is fused together at very high heat. Unlike granite, it resists stains and doesn't need sealing. It comes in patterns and colors that mimic granite very closely, but it is totally predictable, and more uniform than real stone (which might be good or bad, depending on your tastes.) It also comes in colors and patterns not found in nature, like bright blue. It costs about the same as marble or granite. Good luck! Don't forget to seal your marble countertop! You can get sealants at any store like Home Depot. And keep acidic foods away from it.