If battery life is very important to you, good luck with Motorola. My Moto X 2nd Generation probably has the worst battery life of any smartphone I've owned in the past 1-2 years (HTC One M8/M9, Nexus 5, iPhone 6 Plus, OnePlus One, Nexus 6, Note 4, iPhone 5, Lumia 930, Lumia 640) and that is saying something because HTC One's have pretty crappy battery life. Glance screen is pretty horrible and absolutely kills your battery life. It triggers with virtually anything. I've been sitting at my desk typing and it will open up. Now that the display is no longer AMOLED, battery concerns with this are at an all time high (as other tech YouTubers have stated).

I personally don't care too much for battery life since I'm either at work, home or school and it'll be charged up at any of those places -- and quite quickly now with quick charging. Also, I'll charge it in the car while driving or with an external battery and I'm pretty satisfied. It is pretty bad overall though. But Motorola's gestures are awesome and everybody can enjoy them since no other manufacturer really provides such utility or comparable features. Double tap to wake for example isn't available on the Nexus lines (maybe in the Nexus 5 2015 or whatever they call it) but not the 5 or 6. I really love this and after switching from Moto X 2nd Gen found myself tapping my iPhone or Lumia 930 screens since I became so used to it.

I think features/battery life will be pretty comparable overall. Your decision should and will probably come down to price and design. If the new Nexus looks horrible (don't see why it should though) well, the Moto X Pure/Style will probably win. Also if it's substantially more expensive yet more or less the same phone (specs wise), or vice versa.