Yo..

So, I'm building a computer, first time and can't make my mind up on the CPU.

The computer will mainly be used for gaming at 1080p

I've been doing a lot of reading and watching videos and staring at benchmarks to determine the right cpu for me, but it seems the more info I consume the more confused I get.

This is in regards to something like an i5 4460/4690 vs an AMD FX 8350

So many differing opinions and points of view, valid and non valid arguments.

A lot of people say - i5 for gaming, easy choice. But it is really that cut and dry? There is a lot in favor of AMD too.
For example: 120 FPS vs 110 FPS isn't really an argument in favor of a particular CPU because you're not going to notice.

Games are generally GPU dependent anyway, so how important is the small amount of performance that you may or may not gain by choosing an i5 over the 8350. Are you even going to notice such a performance gain?

When people are are claiming Intel i5 all the way, are they really just looking at some benchmark that gives like 5 more FPS and saying yup, why would you even bother with AMD?

This is my first build so I really don't know much on the subject.

Basically, going forward, with games coming out like the Witcher 3 for example is the FX 8350 going to be able to run this at max settings as well as an i5, with regards to real world experience and not just benchmark numbers? I ask because the price difference is quite large and would allow for a better GPU.

What about the consideration of Mantle and games using more cores in the future?

I feel this has gotten long, so I'll stop here. Any more info needed just ask. Thanks for your time.