Core2Duo is the previously generation based on the LGA775 socket. Core i3/i5/i7 are the newest generation of CPU's from Intel. Core i3/i5 are based on the 1156 Socket, and the Core i7's are based on the 1366 Socket (for the most part, there is some overlap). The newer generations will be more efficient and perform better if you compare frequencies only. The Core i3's and i5's also have built-in video chipsets if you plan on using integrated graphics.
What is deference between CPU core I3 and CPU core 2 Duo?Which one is better?Faster?more stable?
Obviously the newer technology has the advantage, better instructions per cycle better TDP, better pipeline usage better for overclocking as well as integrated video on the chip the core i3 performs on par with a very fast E8 series core 2 but for less money and costs less power and produces less heat same for the other chips at other price points