I'm in no means saying that the 5 or 5s or 6 were bad devices. I'm just saying the iPhone 6s is a different kind of beast and is well worth the upgrade from whatever phone you have ...
It just amazes me how people justify the 6S is the greatest iPhone of all time and that the upgrade is the most significant ever.
And I have owned every single iPhone (iPhone 2007-current 6S)
It's because they live in the world today (October 2015)
But u have to rewind history back to October 2013 and history back than said the 5S was the best upgrade of all time for iPhone.
Rewind back to November 2011. Same thing said about iPhone 4S. At first people were disappointed it looked the same. But the 4S went from single core to duo core. Just an absolute monster of an upgrade with duo core.
When you state opinions. U must not rewrite history. You must travel back in time and look at the consensus opinion back than.
Let's look at iPad Air 2 performance. It has 3 cores and 2Gb ram. One task that require multiple cores. iPad Air 2 with its A8X processor performs better than the A9 2015 processor. So 3 cores is better than 2 cores when running task that require it even if the processor is older (both iPhone 6S and iPad Air 2 have same exact 2GB ram).