Whats better i3 or duo core?

The new i3's are still dual core like the core duos, but the i3's will be faster, produce less heat, be easier to overclock, and won't be as loud. I would go with the i3, but for what you're doing I would focus on getting a decent graphics card rather than a faster processor.

I concur with TomTomz. The i3's are a newer and better architecture, which in turn will give you more performance/speed, etc... over the older C2D. For reference check this link out:

http://www.notebookcheck.net/Mobile-Processors-Benchmar...