i shoot with both open. It helps when shooting through a peep with low light, at least i think it helps
I'm one of those who is trying to condition myself to shoot with both eyes open. Right now I'm having a good deal of success with both eyes open at 20 yards, beyond that is quite the adventure
My eyes are nearly equally dominant so I squint my left eye a bit to get the right one to focus through the peep. I always thought I kept both fully open but paid more attention to it while I was shooting last week and just, after 25 years, realized what I was doing.