Most people would never know the difference between them. The 3570K is faster at the same clocks (5-7%), but it's not really enough to matter.
PCIe 3.0 and better power efficiency are what's really important about a 3570K (and the iGPU, if you ever have to use it. HD4000 is quite a bit better than HD3000).
The downside to the 3570K is exactly what socialfox said. When you add voltage to overclock, it gets very hot very quickly. Great cooling is a must for 4.5 and above OC's (better than a 212 Evo, for instance, when a 212 Evo will get you to 4.5, easily, with a 2500K)..