This has very little to do with what the hardware can do and everything to do with what the software can use it for.
android, is not a very nice OS to work with and it is very hard to use the multiple cores. The android developers kit does allow multi-threading, but not true parallelism, and non-optimal multi-threading at that. So what the spec sheet says it does and what it really does are two things.
My point is don’t buy the hype.
All I know is my phone is really fast. That’s all that matters to me.
Without getting too technical, every study I have seen has shown that the average Thread Level Parallelization, (TLP) for ARM cores comes in at 1.4.
This means that only 1.4 cores are doing and the work and in an octo core device 6 of them are just idling 99% of the time.
Not a good use of silicon if you ask me. (BTW I have cored ARMs for ASICs, and they are pricey, but hey Samsung can afford it.)