fnatic :
i5 vs i7 is all about do you have the money? Do you want to future proof your machine? If yes to both then the i7 is the way to go. You will see a 20-30fps increase in your games with the i7 though. BF4 specifically you'll see around a 30fps boost.
That is a totally erronous statement.
1. You will not be futureproof. If you want futureproof, take the most recommended i5 at lower possible price and bundle it with a high end graphics card. Then when new tier of upgrades appear, you can easily upgrade if you feel the need to use more. But do not be mistaken games that will be utilizing 4 cores at 100% and more will not appears until 4-5 years from now.
2. The statement of 30 fps boos from the i5 to i7 is also quite wrong, getting the best FPS possible at most desired settings depends on many factors, but just changing from i5 to i7 cannot give a free 30fps. If that was the case no one would ever buy a 700 dollar graphics card, instead would just take an i7 and pair it with a mid tier 200 dollars card and get the fps that you are stating.