Go with the I5 4670K. About 5% faster per clock so you would have to overclock your 3570K by 200MHz to equal it in speed. Also, for applications, the Haswell is much faster with it's newer instruction set. Plus the Z87 motherboards are better and newer, more of a life time ahead.
We are finally at the point that games are starting to use multiple cores and hyperthreading. With Battle Field 4, the I7 4770K is 27% faster than the I5 4670K. Of course if you do rendering etc. the hyperthreading comes in handy too.