The OnePlus 3 has a 5.5" 1080p OLED display, affording a resolution of 400ppi. For most purposes at least that will easily be sharp enough, but would you have preferred a quadHD display, perhaps for VR, at the expense of greater battery consumption?
I've heard that the reason OnePlus stayed at 1080p was because they felt that the amount of people using smartphones for VR isn't high enough to justify putting a higher-resolution display for VR.
Plus, 1080p is mighty fine for normal use. You still get loads of detail and you can't even distinguish each pixel at a normal operating distance anyway. 400+PPI is more than plenty for daily use. You also have the extra benefit of better energy efficiency, meaning that your battery lasts longer.
Note that SOT is entirely dependent on usage pattern. We can't entirely base a phone's battery life just on SOT alone. We need to know how the phone is being used and how long it has been off the charger since the last time it was plugged in for a full-charge.Battery wise the reviews are showing 3.5 to 4 hours of screen on time which is on par or less than the s7 and htc 10.
To be frank, I don't think we're ready for 4K displays on a phone yet. Improvements in energy efficiency and battery capacity plus performance will have to be made first before it can be feasible to put a 4K display on a phone.I own both a 1080p Nexus 5X with Google Cardboard and a QHD S7 Edge with Gear VR. While the S7 edge does look better, it doesn't look that much better. Both look fairly pixelated. And part of the reason the S7 Edge looks a little better could be because the Gear VR headset is just nicer. Honestly, both resolutions are subpar for phone headset VR, so I wouldn't get your panties all in a knot because the OnePlus 3 screen is only 1080p. Trust me, VR would still look pretty crappy even if it had a QHD screen. Really, a 4k screen is needed if you want VR to look really good from a phone.