At stock both chips will perform about equally.
One buys a "K" for the option to overclock.
If you will be using a Z77 chipset motherboard, you will have the option to gain about 20% more performance.
Pick the 3570K. for the potential.
This question comes with a few side notes, like will you be using a Zxx motherboard? (meaning having the OC ability) But even the Yogscast uses the 3570Ks and they record games in 1080p at the same time. But I found a very trust worthy website for you to take a look at the differences!
At stock both chips will perform about equally.
One buys a "K" for the option to overclock.
If you will be using a Z77 chipset motherboard, you will have the option to gain about 20% more performance.
Pick the 3570K. for the potential.
If price was the same I'd take the 3570k. It will outperform the 4440. The 3570k hits 3.8GHz max and the 4440 hits 3.3GHz. The 3570k is more like 3.7/3.6GHz compared to 3.3GHz of the 4440.
But now you gotta select a Z77 instead of Z87 or Z97. Not as easy to find Z77 or H77 mobos. But possible.
At stock both chips will perform about equally.
One buys a "K" for the option to overclock.
If you will be using a Z77 chipset motherboard, you will have the option to gain about 20% more performance.
Pick the 3570K. for the potential.
I agree with Geofelt, and as of now the i5 3570k is a bit more stable and known chip, compared to the 4440.