The two Core i3 CPUs are 5th generation Broadwell CPUs. The difference is probably 100MHz or 200MHz when it comes to the processor speed. Also, Core i3 CPU lacks Turbo Boost which is basically an automatic overclock when the CPU is being stressed as long as it is not running too hot. Without Turbo Boost Core i3 have lower clock speeds compared to Core i5 CPUs. They have the Intel HD 5500 graphics core.
The Core i5-4520 does not exist so I am going to assume you means the i5-4250u. It is a 4th generation Haswell CPU. There is only about a 5% difference in overall performance between 4th and 5th generation CPUs assuming they run at the same clock speed. The i5-4250u can hit higher clock speeds than the i3-5010u CPU and therefore, it will...