At similar prices, it'd be a tough call between the 83xx and 3570k with a view to the near future imo, that the FX8320 is ~£45 cheaper than the 3570k, I know where my money would be going
Future yes, but for present, it is still -45% or more performance for the sake of -£45 in majority of the games.
To be honest though, I think it might not be a good idea jump on the 8 cores wagon for gaming just yet. Althought I said with the launch of the new consoles, the use of 6 cores or more could become a common standard...but it is still only a "prediction" base on theory. I would say for gaming, i5 is still a better all-rounder. If want to jump on the 6 cores/8 cores wagon, it would make more sense to confirm of the prediction "new consoles=more cores usage" is true two years down the line from now, and then look at what BOTH Intel and AMD have on the market at the time before making a decision which way to go.
If people already got AM3+ board and using an old CPU like Phenom II, then upgrading to the Piledriver would make lots of sense, however if it involves getting a new motherboard, then the Piledriver is not really that attractive comparing to the i5.
If you look at the CPU performance of Crysis 3 for example, it would be a pretty good representation of what the performance of Piledriver 6 cores vs i5 Quad-core:
http://www.techspot.com/review/642-crysis-3-performance/page6.html
The FX8350 at 4.00GHz is only around on par with the i5 3470 at 3.20GHz
And if look at the FX8350 vs i7 3770K, the FX8350 are still quite a way behind when comparing on the same clock speeds. It would be pretty safe to assume that the FX8350 would be close to compariable to i5 if both were on the same clock speed in game that use 6 cores (or may be 1-3fps ahead if the game would use 8 cores), but the trade-off would be FAR lesser performance in games that don't (not sure if it would make any sense at all to "hope for" 1-3fps benefit in games that use 6-8 cores at the cost of having 10-25fps less in games that uses 4 cores or less).