Core 2 Quad. Lacks Turbo Boost and has a higher latency.
i7. Has Turbo Boost which makes it a superior gamer in terms of Clockspeed. Lower latency makes it 40% faster in just about everything. Supports DDR 3 RAM and can take advantage of the latest board that come with USB 3.0 and 6 GB sec SATA.
Overclocking takes care for the absence of turbo.. Latency timings are by design so no comments on that.. However, they play significance only with highly multi-threaded scenarios and/or applications.. If you talk about gaming, there is no such big a difference..
Assuming the Quad Core is a Core 2 Quad Core vs an i7 and remembering that as far as the OS is concerned the i7 is an Eight Core, I own one of each. The i7 eats the Core 2 Quad in every respect. It consistently beats the Core 2 by 40% real time computing. On the Gaming side of things games load faster and hold up much better under intense graphics and action.