Really depends. If you manage to overclock a 3570K to an obscene level then it is a clear winner.
Out of the box, the 3570K is bottom of the value pile because you pay extra for that facility. The rest are generally on a sliding scale, with the cheapest being the best value, more or less.
If you are just looking at out-of-the-box performance, then you can make a case for the 3350P or 3450/3470 as the best bang for buck (3350P is cheapest, but 3450/3470 have a few small advantages which can make them worth the small amount of extra money).