Well a Core i5 is typically a quad core while the Core 2 Duo is a dual core, so the i5 has more cores. As well the i5 is a newer architecture and thus has better performance than the Core 2 Duo.
So to answer the question, the Core i5 is better. By a lot.
If you are buying/building a PC, Core 2 Duo (or Core 2 Quad) is NOT the way to go because its platform is no longer being produced (OUTDATED). Three generations of Intel processors have so far come after the 'Core 2' family of processors/architecture. Buy/build a PC with either a Second or Third Generation Core i5.
NOTE: A First Generation Core i5 PROCESSOR is not compatible with a Second or Third Generation MOTHERBOARD (Second and Third are compatible but for the sake of simplicity, just stick to the same generation of PROCESSOR+MOTHERBOARD).
The Core i5 is much much better and superior than the Core 2 Duo.
Which processor I should buy in i5 family (i5 2320, i5 2400, i5 2500......)
and Which motherboard will be compatible with i5 2500.
Thanks again!!
Sadiq Saeed!!
What will you mainly be using your computer for (e.g. productivity, gaming etc) - let me know your computer use so I better recommend the processor and motherboard you should likely get?
i5 2500 is a great CPU - great for productivity and games. It should handle graphical work (such as rendering) as well, though not as good as the 2600 will. If its just for productivity (such as word, powerpoint, excel) then a basic i5 will be well more than suitable.