I put down "both" because although I was left-eye dominant for many many years, when I was 64 I got hit by a car while bicycling, and got some permanent nerve damage. One of the anomalies of this is that although both eyes still work the same (the left a good deal weaker and less far-sighted), my trochlear nerve got clobbered, and I now see double through most of my field. Each eyeball is tilted down at the center, so I have skewed horizons. My brain, clever brain that it is, decided that the four degree tilt on the right is better than the five or so on the right (edit, Imeant left here) , so switched dominance almost immediately to the right. Now, although my right horizon is nearly as badly tilted as the left, my brain says the right is correct, and attributes all the error to the left. This would have worked better if that had already been my dominant eye, but what I find, rather annoyingly, is that the image from the dominant left eye is laid atop that of the right, so it is harder to disregard. It's taken a great deal of time to adjust to this. Fortunately, the brain can put the images together pretty well for the top 1/2 to 1/3 of the field, at least in the center, so, for example, my view through a car windshield is quite good. I simply have to squint to read the instruments.
Anyway, as a result of this weirdness, I am now usually right-eye dominant, and have begun using the right for photography when possible. I say "when possible" because cameras without a viewfinder diopter may still require the left, or a double check from the left, since my right eye is very far-sighted and the left less so. Of course if the viewfinder has a high eyepoint, I can just leave my reading glasses on.
So for the moment, I'm in the "both" category, though in a couple of years I might end up at the right, or, if I get the slight cataract in the left fixed, perhaps I'll end up back at the left.
One strange consequence of all this is that I cannot trust my judgment of level without a reference. With a digital camera, I have the framing lines actuated. With viewfinders, I have to make sure that horizons are lined up with the edge of the frame and force myself to overlook the fact that a tilt of about 5 degrees looks right.
