Martin, I'm torn between S6 and 5X. On UK Amazon they're about the same price, and I cannot for the life of me decide which one I want. Which would you recommend and why?
Personally, the N5x is better in the following areas:
Stock Android - either it's a factor for you or it isn't
I personally prefer the clean look of stock on the N5x. Touchwiz is better than it used to be but is still a bit gaudy in places although the new theme engine can help.
Radios - I found the radio reception to be abysmal on the S6 one 3g. One went back for replacement and the next was better but overall I found web pages etc loaded really slowly.
Fingerprint sensor - if this is a big thing for you then the N5X is so much better. The S6 regularly didn't work for me where as I'm in nearly every time on the N5x.
Lag - no lag or hiccups on the N5x, the S6 did slow down sometimes.
Buttons - I prefer the soft buttons on the N5x. For me the change in tactile experience on the Samsung with an actual home button and capacitive buttons then the screen all feeling different was something I didn't like.
And the S6...
Screen - is probably slightly better and colours are punchier. The N5x screen is very good though.
Build - I did like the metal and glass and the Sapphire Black looks a really nice blue in some lights.
Cameras - I'm not a photo expert and would say both are good enough for me.
Battery - the battery on the S6 is probably good for 5 hours SOT which is around 1/2 hour better than I've got out of the N5x.
At the end of the day, I've been on board with the Nexus program since day one and this probably sways my thoughts on this device. I also had a Moto X Style in the last 2 weeks and I know I'm going to stock with the N5x for a while after going through the other 2.
Hope this helps. If you are on the fence, go into CPW and have a play and see which you prefer.