The core i3 is a newer processor by intel. It runs at 2.13GHz and has hyperthreading. This means it will likely perform better at multi-tasking than a core 2 duo at a higher clock rate. The thermal design power (directly related to heat and power consuption) is 35W.
As for the core 2 duo, you failed to tell us which model you are comparing the i3 330m to. If you are comparing the core i3 330m to a similarly or slightly higher clocked core 2 duo, it would be more powerful, especially, as I mentioned before, in multi-tasking.
I believe if you are comparing the i3 330m to a core 2 duo at 2.3GHz or higher, then the core 2 duo would be the clear winner. But do not forget to take into account hyperthreading. The core 2 duo does not have this feature.
As for power, the core 2 duo is different with each model, ranging from under 10W TDP to 40W TDP. I managed to find this:
T models: 30-39 watts
P models: 25 watts
L models: 12-19 watts
U models: <11.9 watts
The core i3 330m is a newer processor. But it does not outperform last generation's mid to high end processors. If it outperforms a "core 2 duo" will depend on which model and speed of the core 2 duo. As I said before, I would get a 2.3GHz or higher core 2 duo in my notebook rather than a core i3 330m. But anything below that, get the i3 330m.
Werxen seems to be trying to make a sarcastic joke. I don't understand why though.