Core 2 duo is a processor brand. dual core is a broad type of processor. The core 2 duo is a dual core processor. Look up multi-core on wikipedia. If you tell us the exact model of each processor you are looking at we can better help you. perhaps you meant Pentium dual core. The brand is also not the only factor. You will need to give us the model which will tell us the clock speed and other important performance related details.