Not sure why you have to choose. Just have the laptop with your preferred video card have the i7 placed in it. Your best bet for i7 is the 820QM not the 720. The 820 has more l3 cache. Don't get hung up on clock speed. The 820 is going to be more efficient. If you cant go for the 820 then consider the i7 620 dual core. It has 4MB of L3 which is the same amount as the 820 when you figure one is a 4 core 8 thread and the other is a 2 core 4 thread. The 620 is going to be a good $200 cheaper than the 820 yet you get the same L3 cache. Any decent custom laptop place should be able to give you any CPU you want in the video card of your choice. It was only mentioned once but you keep in mind, the level of video card you are looking at are not made for MXM modules, this means no upgrades to another video card. So go with the video of your choice then have them upgrade your CPU. You can upgrade the CPU on these level of quality laptops but not the GPU.
So unless price prevent you from doing anything else, try the 2010 i7 620M rather than a lower l3 i5. If you have the money to go 4 core then jump over the 720 and go to the 820QM. Don't bother with the 920. It has the same l3 cache as the 820. The clock speed difference wont help you since you will running at some form of bottle neck before too long anyways. The other big benefit to the 820 as compared to the i5 or 620 is the 820QM can use MHz DDR3 RAM as compared to 1066MHz RAM.