they are the same chip, except one has a higher clock. BUT if the chips are binned, the likelyhood of the max clock on the 8350 is likely to be higher than the 8320 on average. but if you come across a good 8320, then its exactly the same.
basically luck of the draw. the 8350 is just more likely to have a better chip, but doesnt necessarily mean that all 8320's are worse than it.
They are exactly the same chip. Actually I remember last year that people were getting higher frequencies out of the FX 8120 than the 8150. But I can only overclock my 8120 to 4GHz and keep it stable. Anything more and it just gets too hot. So yeah. It's the luck of the draw and you might have more luck overclocking the 8350. That's the absolute only possible advantage though. The 8320 should easily clock to default FX 8350 speeds.