What happens when 8 cores becomes a common thing though?
Then the FX8350 looks really good.
Look at it like this:
The i5-3570k is good for what is here right now, and it will probably be decent for a while. Though, if you want to upgrade later it will be a complete overhaul, as the LGA 1155 socket is going to be dead when haswell arrives.
The FX8350 is only starting to see games optimized for it, and games are continually moving toward more cores with each new release that comes out. If you want to upgrade your AMD in the future, your AM3+ motherboard is supported fully through the next generation of AMD hardware through 2015.
Food for thought.
If you want to have slightly better now, get the i5. If you have an eye toward the future and want to upgrade later with lower costs, get the FX8350. The difference at this moment is negligible between the 2.