With magnified optics a larger field of view is absolutely desirable. Even shooting with both eyes open that larger field of view (FOV) lets you see more through that magnified window. Sometimes with red dot sights (RDS) we shift all of our focus to our dominant eye, a larger window can be beneficial. Dave Merrill and Roland the Terrible pointed out a larger window is more forgiving in both finding the dot and in shooting from unconventional shooting positions where you to not have that perfect cheek weld. RDS have some added benefits due to their lack of magnification; our field of view with an RDS can be what we see with our two eyes.
Because we have binocular vision the Bindon Aiming Concept applies. This concept requires both eyes to be open to let your brain superimpose the dot on your target when changing your focus to your non-dominant eye. If it sounds too good to be true – try it out yourself. Cover the exterior lens of your RDS and aim with both eyes open. Although you cannot see through the optic, the red dot appears on what you are aiming at. Please note this may not work if you have eye issues.
Typically when shooting an RDS our vision is not restricted to the window -instead that window is just a place for the dot. Think of it like a heads up display. The placement of the RDS can play a part- closer to the eye seems to have a greater perceived FOV for some. (Previous piece on optics placement: https://primaryandsecondary.com/accuracy-and-optics-placement/) If the size of the window was an issue RMR’s would not be as popular as they are. Just remember you are only looking through your optic when engaging targets; otherwise you are looking over your optic when you are looking for targets.