They're the same cpu with the same L1 and L2 cache except the 2.4GHz is 200MHz faster than the 2.2GHz one. As far as the GPU. The 128MB 8600GT has lower clock and memory speeds than the 256MB 8600GT, but that really won't make a difference especially if you're doing photo editing work. If you're not going to dual boot and game on Windows then don't bother with the high-end Macbook Pro.