Unfortunately because of the split contract people will have to acquire multiple samples before they can be sure to TSMC's and Samsung's A9 for comparison purposes.
You were vocal in stating that A9 is all TSMC because of superior yields and that Samsung is out of the picture due to very bad yields. Now you say Apple has split the contract between Samsung and TSMC and thus we have to source multiple samples to confirm if there are multiple A9 chips. Anyway we are getting a clue that A9 for iPhone 6S has gone to Samsung and A9 for iPhone 6S Plus has gone to TSMC.
Chipworks iPhone 6s teardown
http://www.chipworks.com/about-chipworks/overview/blog/inside-the-iphone-6s
"First off - Apple’s new A9 processor is the APL0898, and it’s ~8.7 x 10.7 mm, or ~94 mm2, which agrees with our 80% shrink guesstimates. Maybe that’s a reflection of the 14/16 nm processes only shrinking the transistor dimensions, not the metallization, maybe it means that Apple have crammed more in there (probably both). And it seems to confirm our postulated 8MB of L3 cache."
"The APL0898 size fits with an 80% shrink on the A8, and seems to have 8 MB cache - and our first look leads us to believe that our sample is from Samsung. "
iFixit confirms iPhone 6S has APL0898 (likely Samsung) while iPhone 6S Plus has APL1022 (likely TSMC). Normally the smaller iPhone model sells twice the units of the larger Plus model. This would mean Samsung gets the bulk of the volume this generation.
https://www.ifixit.com/Teardown/iPhone+6s+Teardown/48170
Step 17 - Apple A9 APL0898 SoC + Samsung 2 GB LPDDR4 RAM (as denoted by the markings K3RG1G10BM-BGCH)
https://www.ifixit.com/Teardown/iPhone+6s+Plus+Teardown/48171
Step 12 - Apple A9 APL1022 SoC + SK Hynix LPDDR4 RAM as denoted by the markings H9HKNNNBTUMUMR-NLH
So from first appearances it looks like Samsung and TSMC got the A9 with Samsung getting the bulk of the volume at 65% given the sales split.
With this split atleast within the iPhone 6S there will be no variances in efficiency and battery life. It does not make sense to have 2 different suppliers with different processes to supply chips for the same device. Apple has made a logically consistent choice.