i5 4690k is better for gaming but also more expensive than FX8350.
FX8350 on the other can run better on certain programs or games which can gain advantage on more cores than faster cores.
If you need both fast cores and more cores/threads, i7 4790k or E3-1231V3 is more interesting to you.
Intel procs have the better thermal dissipation and power management too.
Deciding between AMD and Intel today is more related to budget or to pure fanboy-ism.
I have been switching or building my rigs since years between AMD and Intel, few of my rigs was even outside AMD and Intel namely VIA Cyrix.
I would say, if you wanna pure performance, Intel is the way to go today.
AMD was good, FX8xxx was good at launch but AMD unfortunately still does not bring anything new to the market since then. The architecture starts to be out-of-date in my opinion.
About DX12, I dunno yet if DX12 can make the FX8xxx perform better, we have just to wait until DX12 really used in games. All the things people said about DX12 and AMD procs and GPUs are pure theoretical and speculations for now, only real life will tell the truth. This is why I am very excited about Win10 and DX12.