The 8x42 and 10x42 pair is the most common decision in binoculars, and it is genuinely close. They gather identical light and differ only in how that light is used, which means the right answer depends on what you point them at.
What eight times gives you
A wider field, a brighter image, less shake and a 5.25mm exit pupil that works at dusk. For woodland birding, for anything moving, and for extended handheld use, this is the configuration that wins, and it is what most experienced birders carry.
What ten times gives you
More detail on a static subject at distance, at the cost of about twenty per cent of the field and a noticeably dimmer, shakier view. For open country, waders, raptors and distant landscape detail it is the better tool, and it sits right at the handheld limit.
Twelve by forty two and beyond
A 12x42 pushes past comfortable handheld use with a 3.5mm exit pupil that is dim at dusk. It exists for people who will brace or mount the binoculars. If you find yourself drawn to it, the honest options are image stabilisation or a tripod, not more magnification in the same package.
Questions people ask about binoculars
Is 8x42 or 10x42 better?
Eight for a wide bright steady view and for moving subjects; ten for detail at distance across open ground. They gather the same light.
What are the best 8x42 binoculars?
Any fully multicoated pair with BAK4 prisms, comfortable eyecups and enough eye relief if you wear glasses. Above that price band the gains are in edge sharpness and build.
Are 12x42 binoculars too much?
For handheld use, usually. The exit pupil is small and the shake is visible; the same money in a 10x50 gives a brighter, steadier view.