the cpus itself are not $20-30 apart unless in a different country and in that case no brainer the i7, but being the $120 difference for the cpus in the US its a different debate as the price is quite higher, i mean u can get a 8350 and decent board for the cost of the 3770k.
The 8 cores are basically 8 cores with shared resoruces etc, and being competely different but similar to intels HT, but intel doesnt label their cpus as 8 cores. Intel has 4 cores with 4 HT cores or logical cores, where amd has 4 modules with 2 logical cores per module, so being unlike intel almost every program that can will see and spread use across all eight cores as HT some programs may not recognize or use all 8 cores in a i7
Not saying the 8350 beats the 3770k but for its price point is a competitor, unless the above being a $20-30 difference.
Also there are some benchmarks that the fx beat the i7 but is only like one, and more often not terribly behind it, everything is situational in its performance but obviously for a general any purpose intel is a sure win