The Intels can process more instructions per clock, which is why a 4 core i5 can beat an 8 core fx, especially in lower threaded apps like games. You can't just look at clock speeds when comparing cpus that use different architecture.
Think of it this way, putting a V8 inside a Porsche, and putting an identical V8 inside a Ford pick-up - Guess which one is going to go faster?
Obviously this is just a silly example, both are good, but specs wise it's almost impossible to compare two completely different architectures. Not just for CPUs either, the same applies to GPUs.
Intel generally use 'faster' cores, despite the lower clockspeed. Clock speed only measures how fast something can go, it doesn't measure how fast it actually is. Another example for this could be: get The Mountain from Game of Thrones to throw a brick and, at the same time, get Geoff from Costco, who likes skinny latte's and late nights in watching Netflix, to throw the same brick, from the same point, with a run-up. Guess which brick lands the furthest.
Think of chip architecture like the blue prints to two buildings. Both different. Both buildings. One might be layed out better so it's easier for people to get to the main corridor. Where-as the other one features many more rooms.
Honestly, I really should use these examples, but they make a good representation.
The 8320 is a good CPU, it uses less powerful cores by comparison to Intel but it still gets the job done. Price usually is decided by performance value and/or the cheaper company doing their best to under-cut the more expensive one.