When I'm hiking, weight is not as important a consideration as size and ease of handling. Binoculars are light weight compared to everything else in my pack, but I like them to be small enough to be able to keep them on a strap around my neck at all times, but have the option of tucking them into a smallish vest pocket or under a strap (with the bino strap still around my neck) to keep them from swinging around and getting in the way when I'm using a camera or doing things like catching lizards by hand. It is important that they hang flat against my body so they don't get in the way when I'm juggling other equipment (camera, field guide, backpack, etc). So I prefer a compact 8x32 roof (e.g. Zeiss 8x32 FL), or a premium pocket roof (e.g. Leica 8x20 Ultravid BL). The latter is smaller and lighter, but sometimes that is not an advantage when hands shake during strenuous hikes.
--AP