I have noticed that some intel i7 processors have lets say a 2.6 gigahertz frequency, while an i5 processor may have 3.1 gigahertz with the same amount of cores. Why would the i7 be better?
For most people, the i5 wud probably be faster !!! Only a few software, like rendering and video encoding etc, can make use of all 8 threads of the 2.6GHz i7, to get a slight edge in performance over the 3.1GHz i5
At the end of the day, i5 or i7 are just branding schemes, compare the i3-560 with the i5-650 for example. Basically the same chip sold for $40 more!!
PS:- My female friend got a expensive laptop with a 1.67GHz i7 (45nm, 45W). All she ever does is watch movies, listen to music and browse the web!!
She cud have easily taken a 2.34GHz i3 (32nm, 35W), even with 2 cores less, that 50% clock speed advantage wud have definitely been of more use to her
probably even given her longer battery life
So just buy whatever suits ur needs, and don;t bother with the branding:)