You don't make a difference between CPUs by their clock speed, number of cores or socket type but by their architecture, requirements, etc. If you're using the FX-4100, it's gonna perform certainly a lot worse than the i5 3570 because of the architecture which is totally different as you can see by the huge difference in price. The 3570 has a larger L3 cache and you might know that the larger the cache, the faster the CPU usually is. For a budget gaming build, I recommend you getting the i5 3570 but if you wish to get good enough performances for about 70 pounds lower, then go for the AMD