The Dual core has less cores but faster speeds. You can probably get away with the Dual core but don't expect to get awsome performance from either CPU. Most people are using quad core processors that are running anywhere from mid 3 Ghz to 4.5 or slight higher overclocked.
Based on the model of the processor it will comes with Intel® Turbo Boost technology. This technology will clock the speed of the processor up based on how hot you are running and how many cores that are being used. With the 2nd generation Intel Core i7 processors like the Intel Core i7-2720QM you will always see this Turbo Boost giving some performance boost to the processor and if you are running a single threaded application you can see it running up to 3.3GHz.
While a dual core Intel Core i7-2620M may run as fast as 3.4GHz with Turbo Mode. In the end the real factor is how many threads you are currently going to be using at once to determine which is going to be faster.
Thanks for the feedback, but I have a budget of just over $1000, and I'd like to keep it under that amount. I'm just wondering if a 2.2 ghz quad core would fit the requirements for a 2.4 ghz game without overclocking.
The problem is that it is a gray area. The processors rated speed doesnt technically meet the games specs but rarely does it not run at that speed or greater. So for me I wouldnt have a problem running it on a laptop with the Intel® Core™ i7-2720QM but since the program in question may not see the processor running at its requested speed it may lead to a problem with that application.
If I were you, I wouldn't even look at the i7's. A dual core i5 will do just fine and your battery life will improve enough to be significant. If we're taking about laptops, one of the most important factors is portability, that comes down to the weight and battery life of the laptop.
And in most games, you will be bottlenecked by your GPU, unless you use an external one with an expresscard adapter.
Go for the one that will eat less juice.
That's my 2 cents, but I am a person, that can play portal on a x200s.
And I still have my desktop for serious gaming.
I think your question will largely land upon, if the game is requiring 2.4 ghz is it optimized for dual core or quad core? if the game wants 2.4 ghz dual core and is optimized for dual core, then a quad core that is 2.2ghz should be able to handle it as said above with turbo boost.
Let's say I'm running the game along with 2 windows, with 2 tabs each. Would it still cover the game requirements?
If you are running the game then your other 2 windows are probably not doing anything and thus won't have an affect on your game. OTOH if you have some windows open doing downloads, virus scans, etc. then that WILL affect your game.
I have 2 machines that I use every day, one with a dual core and one with a quad core. The dual core processor is a faster processor, but sometimes slows down when there are several things actually running at the same time. My quad core machine does not slow down when I have multiple things running. I can be using the machine and it is running fine and very responsive, and only later do I find out that I had a virus scan running in the background the whole time.
I think power users should have quad cores in their desktops. Laptops are a different story, since there are battery life and heat implications with more cores in a laptop. But only you can weigh the pros and cons and pick.
Oh and as mentioned, you have to find out if your games can use multiple cores. You could have a lot of cores but if your apps don't make use of them then your apps won't benefit directly from a lot of cores.