Envy 15 i5 vs i7? What gaming performance difference will I see?

What the topic says.
Going to buy an Envy 15 and was wondering what kind of performance increase I will see from an

Intel(R) Core(TM) i5-460M Dual Core Processor (2.53 GHz, 3MB L3 Cache)

vs an

Intel(R) Core(TM) i7-720QM Quad Core processor (1.6GHz, 6MB L3 Cache)

Thanks.