Would i7s offer a significant increase over Core 2 Duos?

[G2K]

I'm in the market for a laptop (I know Dolphin isn't the best on laptops), I want to know whether or not I should shell out the extra money to get an i7 mobile or if it will barely be different than the C2D when it comes to Dolphin. This is basically the deciding factor of my laptop, which I need to buy ASAP, so the quicker the response, the better. Thanks!