As I look through the CPU forum section I'm struck by the number of threads that ask "Which is Better 8350 or the i5-4670k ?" No matter how many times this question is discussed in a thread we still get people asking this question and there is not going to be any different answers because the facts and the benchmarks are out there. People are using these processors in their computers to game with and are having good success in doing so.
Step 1. The budget, this will determine a lot for some people because if the budget is low then you don't really have much choice. If you budget is such that you can afford about $200 for a CPU then you do have to seriously consider the AMD FX-8350 since it comes in just under that $200.
The 8350 is an 8 core CPU with a base clock of 4ghz and a boost clock of 4.2ghz and it competes very well against the i5-4670k and i5-3570k both of which cost more than $200.
However in most gaming benchmarks the 8350 will come in behind the Intel CPUs.
Step 2. The Intel i5's. There are two very good Intel i5 CPUs that are very good for gaming and the i5-4670k which is an unlocked CPU will give you a better gaming performance then the 8350. However your budget will have to be able to accommodate an additional $40 over the 8350.
What you'll get is an unlocked multiplier on the CPU that will allow you to overclock it and it's a quad core vs the 8 core 8350 which can also be overclocked. The i5-3570k can also be considered here and it is only $20 more than the 8350 and will give you the same unlocked multiplier and is also a quad core that will perform the same of better then the 8350 depending on the game.
Step 3. Power consumption, it might not be a concern for some but when you have to pay your electric bill you may want to consider how much electricity your computer is using and all the components will use some power to function. This is an area where the Intel CPU will help pay for the higher price tag , although it may be over a period of time for it to do that but the 84w i5-4670k will use a lot less then the 125w 8350. So for every hour that the computer is on you are saving that 40w difference in electricity cost it will amortize that additional cost over time. It don't help you with the initial up front cost but the overall cost to run it will be less.
At some point games will begin using more then four cores and then the 8350 will make a lot of sense and if Intel doesn't start making six and eight core medium prices processors that the lower budget computer builder can use for his gaming machine then AMD will be alone in that market segment. Currently Intel does make a six core CPU but the lowest priced one is $500 and that makes it only practical for a high end gaming machine.
Conclusion. The choice for a gaming CPU would be the i5-4670k and if the $40 is going to break the budget then go with the i5-3570k which is only $20 more then the FX- 8350.
Brand preference is something that can play a part in the choice here and if you really want the AMD processor then your not making a big mistake because benchmarks show that there is not a lot of separation between the two and you will get a competitive CPU for that $200.