Each device was cleanly restored to iOS 9.0.1. They have the same capacity (128GB) and the exact same process was used to setup iOS.
As expected the iPhone 6s came in first place; however, the iPhone 6s Plus strangely came in last place. We repeated the test numerous times with the same result. Last year, there were reports that Apple was having issues with the TLC NAND Flash in the 128GB version of the iPhone 6 Plus. Perhaps, the company has made a change to the storage with the iPhone 6s Plus. We're looking into the matter and will let you know if we learn any more details.
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