Which one? Title says it all really. Money doesn't matter since they are both the same price and power usage doesn't matter. What matters to me is really just temperatures. Is PCIe 3 and the other features of Z77 worth the higher temps?
More about2500k 3570k
The 3570K only reaches higher temps when it's overclocked to silly speeds. PCIe 3 doesn't really matter yet, although there are a selection of graphics cards that have it, they don't really need or use it.