Ivy bridge i7 3770k vs i5 3570k

I think that the 3770k is hyperthreaded, which means that four of its eight cores are virtualized--they don't physically exist on the chip, but are rather the product of some tricky data handling that the chip does. The 3570k just has the normal four physical cores.

Hyperthreading will only make a difference in programs that are designed to use it well. Programs that already scale their performance across multiple cores (like video editing and some design programs) will get a boost in their performance from the 3770k. You are giving them more cores to process data with.

However, most programs can't handle hyperthreading very well. Almost all games can't. It can actually hurt performance in these cases. So the 3570k will run just as fast if not faster (disregarding different clock speeds) as the 3770k in most cases. Plus it's cheaper, and so it's the better buy.

If you edit video for a living, get the 3770k. Otherwise, get 3570k.

*Note: This is all speculation based off the published differences of the chips, based on the 2600k vs 2500k debate. Ivy Bridge hasn't actually been released yet.*