He’s not wrong when it comes to magnification versus handheld stability. Depending on the person, they will likely see more detail through a handheld 6X, 7X, or 8X than a 10X, 12X, or 15X due to less image disturbance from shaking. Again, this is offhand. A tripod or image stabilization obviously changes things. Field of view and depth of field are also superior with low-power binos.In addition, stay away from 12x on your chest, especially if you have a spotter.
8 or 10x.
For use inside one mile, with most glassing under 500 yards, I think the OP would be better served by an alpha-level 8x32 than upgrading his 10X. They are marvelous instruments that are smaller, lighter, and better in many ways than 42mm class binos.
Having compared 8X versus 10X on a variety of hunts around the world, for a one-bino hunter, I believe 8 is superior mainly due to less image shake. Out to a mile or mile and a half, both 8 or 10 works fine.
When you get to distances where 8X fizzles, the answer isn’t to boost magnification 20% to 10X. The real gain comes from jumping to 12X or 15X and a tripod. This gives you optical horsepower.
My ultimate combo would be a Swaro 7x30 EL Range (doesn’t exist) for handheld use with a 13x50mm alpha-class big eyes for distance work.