zeiss monocular vs binoculars

Obviously a monocular is smaller and lighter than the same size/power binocular. The disadvantage is that you lose your 3d vision, in other words the sense of deph. To some (like me) a monocular is also harder to hold steady and to quickly find the subject.
There are a few possible explanations why you close one eye. The most common is that you are not focusing your binos correctly. You need to start with the dioptric correction set on zero, focus looking through the left eye covering the right exit lens ( so that the right eye is still open but cannot see through it…) Then cover the left exit lens and focus using the dioptric adjustment (usually marked -2/-1/0/+1/+2)
Another likely cause is that your binos are out of collimation, the two lenses point at a slight different angle. As with the focus test, point them at a well defined subject, a sign with writing is the easiest, and alternatively open and close your left and right eye. If you see a different image , you binos are out of collimation. Very common with cheap binos.
Franco

I purchased a Minox Monocular last year and have brought it with me on a number of hiking and paddling trips. The advantage kayaking is obvious – keeping one hand free to hold the paddle is important in rough seas – but it is also a great tool for walking. I keep it in an outside pocket of my pack or shirt so it is used far more than a pair of binoculars tucked inside the pack. Field of view really hasn’t been too much of a concern for me in that I’m looking for landmarks, checking out a bear or wondering if that bird is an artic or common loon. My Ziess Victory Binoculars are light, but the monocular is ultralight. Go with the monocular, but make sure you buy a quality lens; the Ziess is a good bet. Stay clear of the Brunton $29.95 monocular.

Whatever you find most comfortabe, as long as it has high quality lenses.