Get the Core i7. The math is very compelling for the $200 you will spend. The Core i7 has a 4.6% faster clock speed and it has TWICE the logical cores.
A faster dual core CPU (the Core i5) will usually beat the 4-core (Core i7) in gaming performance because you can purchase it at a faster core clock speed. However, Apple is not doing that here because it's confusing to consumers. You can buy a 3.6 GHz Core i5 on the open market it just isn't an option here.
Basically it's an apples-to-apples comparison at the same clock speed, until you come to hyper-threading. The Core i5 and i7 have the same Turbo Boost mode features, memory bandwidth, and so forth. The Core i5 just doesn't have hyper-threading. If you were doing 3D modeling, CAD, or video editing, you'll see a significant boost from a Core i7's hyper-threading, even if you had a faster clocked Core i5, because it would be like having two Core i5's to that software!
Now, for compiling code or Photoshop, you want an SSD and a lot of RAM. However, the SSD can be extremely expensive. But believe me compiling code on an SSD will spoil you. My buddy at work has his desktop set up with the 80GB Intel X25M as his boot / compile drive. It's a VAST, VAST improvement over a spindle. If your time is money, you can justify that.
Hope this helps.
