Apart from the size is there any major differences between the iPhone 6 and 6s?

Apart from the size is there any major differences between the iPhone 6 and 6s? - 1

None at all other than size

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The size is barely any different actually.

Could check GSMArena.com & compare them for a detailed look at the difference.

I think you are thinking of the 6 and 6s vs the 6+ and 6s+
the main difference between the 6 and 6s is the 6s can be unlocked to more phone companies