With hiking binoculars I'd worry about weight before optics. The glass that shows you a hawk on a snag or the route up the next ridge only helps if it's in your pocket, and most binoculars are built for someone standing next to a car.
So this page only ranks binoculars small enough to carry all day: pocket 8x25s and 10x25s that weigh under 13 ounces, and compact 8x28 to 8x32 models that weigh a little over a pound at most. We ranked them on weight and size first, then on how bright and sharp they are for that size, then on eye relief, field of view and weatherproofing. My dad and I haven't bench-tested any of them.
The order comes from each maker's published specs, independent reviews from Audubon's All About Birds and Field & Stream, and what Amazon buyers report after using them. Review counts only back up the order. The Nocs has the most ratings here and finishes seventh, because its short eye relief shuts out anyone hiking in glasses.
One note on the ceiling. Swarovski's CL Pocket is on this list, and it sits at the very top of what a pocket binocular costs, alongside Zeiss's Victory Pocket and Leica's Ultravid, which are not. Expect roughly $900 to $1,100 at that tier. The money buys a brighter image that stays sharp out to the edges. It doesn't buy a lighter binocular: the CL Pocket weighs more than the Zeiss Terra ranked above it.