The greater the magnification, the harder it is to keep the image steady. (It's one reason the army use only 8x binoculars). Forget 16x and 20x for hand-helds.
There's only a fixed amount of light entering the object lens, (that's the one at the front). The more the image is magnified, the more the light is spread out, and the dimmer the image will be. So the bigger this front lens is, the more light gets in and the image will be brighter and better. It's the principle behind 'night' binoculars. (Those humungously big binoculars that were used on old battleships were only 3x magnification! But the image was so bright and clear that signal flags could be read where only the mast of the other ship was poking up over the horizon.)
Form these reasons, a pair of 7x50s can give better results than than 10x30s, for example.