The exynos is largely a stock A15 implementation. There is much more design in the Swift A6 core than there is the exynos 5 core. Most of Samsung's work went into the memory hierarchy.
That being said, there's nothing spectacular about Samsung's designs. In fact, most of the design wins go to Nvidia, who can leverage their own graphics IP and have been forward thinking with their shadow core, or Qualcoomm, who has been doing custom ARM architecture implementations long before apple did swift.
Samsung has also yet to fit Exynos 5 in a phone or even a phablet. Thus, it's clear it wouldn't have been ready for the iphone 5 and it hasn't proven itself as a phone processor yet at all.
Although I can find no literature on the die size, you're looking at the issue wrong. Power is a combination of process, transistors, transistor type, operating frequency, dynamic operating frequency, core voltage and power saving implementations that can be transistor level logic implementations or endemic like power gating and declocking. It also depends heavily on what fills the area such as cache, core logic, memory bus, etc. Different areas see different toggle rates, and hence, more power draw.
A15 is no doubt more powerful than the A9 and recent custom implementations of the ARMv7s ISA, but they're starting to add a lot of fluff phone processors don't need. ARM is looking to take on Intel in the ultrabook/notebook and eventually even server space with their recent 64-bit processor announcements. Not really what Apple needs in a phone processor. ARM's introduction of the light A7 core is in fact a reflection of the fact that can't do a one size fits all approach with the A15.
It's also important to remember, as was noted, that their clocks are 25% higher.
The iPad needs an X processor because it has more pixels to drive. The touch has an older processor because it's inherently a much more low margin device. Also why it has a worse camera and a worse screen.
TSMC doesn't have a 32nm node. They skipped it. But yes, generally "half-nodes" do retain rules and a simple optical shrink is usually doable.
" posts when iOS went to Apple Maps.
