What is better? Intel Core I7 vs Intel Core 2 Duo

The i7 is a quad core processor, while the Duo is dual core. Quad core processors have two dies, each with a dual core processor...the Dual core has a single die with a single dual core processor. How do you plan on using your laptop? I think, for most consumers, the dual core processor is more than enough, especially if paired with decent RAM...and won't cost an arm and a leg. Yes, the i7 is faster than the dual core.

I too am thrown off a little bit... not so much over the ghz but over the labeling of it. My new XPS 1640 T9600 is labeled a *2.8ghz* processor... but Windows and Speedstep usually keeps it at half that (1.6ghz) and revs it up to 2.8 when it needs to. The i7 720QM is labeled 1.6ghz with 2.8 "turbo mode".... now I've read all about the turbo mode and it's very interesting (and complicated). But, does this also mean that the i7 720QM actually normally operates at *half* of 1.6ghz and actually can go through 3 different modes (1ghz, 1.6ghz, 2.8 turbo mode)???

In terms of snappiness/responsiveness (not just long drawn performance like video encoding) like switching windows, launching apps, etc. is the t9600 actually a bit bettter than the i7? I think it would be, but I do not know.

I plan to use it mainly for college.  I am curious because I also want it to be able to games that require faster processing.  Also, i want it to last for at least 5 years so it can get me through college.  I dont want to buy a computer that is outdated within two years.  I am looking to spend about $1300.