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.