Sorry I mistyped. I went in surprised that one version isn't dedicated to a device. From what I know the performance and other characteristics are slightly different and may better suited to one device than the other.
You would think that the lowest power / leakage chips would go their smallest and most popular device, the 6s obviously! In an interview regarding 10nm, senior TSMC employee Dr. BJ Woo stated " Another 10nm challenge is that resistance goes up significantly as metal layers scale down. Selectively relaxing the metal pitch provides a way to optimize performance versus density. 10FF allows the designer to make this kind of adjustment in order to find the best tradeoff."
Perhaps TSMC have traded overall density for lower resistance / leakage, compared to Samsung. Pure speculation, of course.