The only other real performance difference would be integrated GPU; the Intel HD 2500 in the i5-3570 and the Intel HD 4000 in the i5-3570k.
If you are going to be installing a graphics card to play games, then the performance difference is zero. While the Intel HD 4000 is definitely more powerful than the Intel HD 2500, it is slightly slower than a desktop Radeon HD 5550 GPU. Both are fine for watching HD movies though.