The i7 will definitely be the better performer over all. However, it could cost you more, and will probably use battery juice more.
If you're not looking for extreme energy efficiency (in that case you'd want a Netbook with Atom processor anyhow) and don't mind a higher price, then i7 is the better one.
If they're about the same price anyhow, I'd go for an i7. Also keep in mind the graphics processing ability of the laptop. The Core 2 Duo with a real graphics card installed, would perform better overall compared to an i7 with integrated graphics if you see what I mean.
But if you can get an i7 with a graphics system (nVidia or ATI, not Intel) it'll be pretty nice.
For instance, they claim you can run Crysis on LOW settings @ 44.3FPS.
Or Call of Duty 4 on LOW @ 73.3FPS, or MEDIUM @ 30.6FPS.
They're rating it very close to the nVidia 8600M graphics chip.
With laptops you have to realize that even a good gaming laptop, will never perform as well as a good desktop system. You just can't pack the same kind of power into a laptop that you can into a desktop. So you won't be playing games at max settings, let alone high resolutions.
As far as mobile graphics cards go, the 4530 is a fairly basic GPU. It's sort of the 'entry level' gaming option if you will. Mobile graphics cards tend to be fairly expensive, so getting a 'high performance' gaming laptop can get fairly expensive.