You seem to have already included the important differences:
i5-3570k is Ivy Bridge, LGA 1155.
i5-4670k is Haswell, LGA 1150.
The 4670k offers somewhat better performance and power consumption, but slightly less overclockability.
Differences between the i5-3570K and i5-4570K are difficult to spot. I think there are improvements in Haswell virtualization and vector manipulation, the HD4600 integrated graphics, and other details. It's interesting that Haswell was touted as more energy efficient, yet, the i5-3570K is rated at 77W and i5-4570K at 84W.
Below are posted the ARK site specifications.
These appear to be extremely similar, you may want to compare also with i7-3770K / i7-4770K which is 3.4 / 3.9GHz, has more cache, and most importantly is hyperthreading > 4 cores / 8 threads. In the US the i7 costs about $120 more and depending on your applications, may be a better long-term choice.