You basically have two choices Ivy Bridge i5-3570k (socket 1155) and Haswell i5-4670k (socket 1150). They do not share the same socket which means they do not fit in the same motherboard.
Haswell is on average 5% more powerful than Ivy Bridge at the same clockspeed. Based on a lot of posts, the overclock limit for the i5-3570k is about 4.6GHz or 4.7GHz. Based on the few post I've seen Haswell is so limited to being OC'ed to 4.3GHz.
Socket 1155 is dead, socket 1150 will live on into next year when Intel releases Broadwell. In 2015 Intel will introduce yet another socket for Skylake and it's 2016 successor, Skymont. In 2017 Intel will launch the successor to the Skylake/Skymont with yet another CPU generation and a new socket.