Why is the G4 out? If their claims of better screen, camera and battery play out then the S6 isn't doing anything better. These two devices are both very similarly competitive from what I've seen with LG and the G4 claiming to push further in almost every category. These both seem like they could end the year in the top 5 android devices this year.
Nexus 6 Assassin Edition. Android Central Moderator.
I'm pretty much posting in an 'in my opinion' mode. In the case of the G4 I gave the S6 better marks for physical design, preferring TW over LG UI (although not a huge fan of either, I dislike LG's more than Samsung's), and preference for the Exynos chip this time around.