Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Get the one with the i5!

Main reason, the older one does not support on access graphics switching meaning to switch from the 9400 to the 9600gt you actually have to log out of the machine and log back in after clicking a switch in settings. The one with the i5 and 330m gt will switch on the fly without you needing to do anything.

Google "Optimus" to read about the switching tech. It will be much less of a hassle for you with that one I think.
 
I'll also suggest the i5 machine over the C2D machine.

Reasons:
* Faster CPU
* Faster GPU

Good luck. :)
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.