Highest Quality (April 2019)
My preference has been the Zeiss Victory line of optics because of their razor sharp image with the highest light transmission, and a wide field of view. But today there is little difference between the top-notch binos of Zeiss, Leica and Swarovski. Swarovski has been known for their very good service so they have become the most popular brand in this segment in many countries. I find the size and feel of the Swarovski 8x32 to be the most comfortable, and I do not miss any light from the 8x42 which is arguably the optimal version. I find the 10x version to loose in detail due to handshake (I cannot hold it steady enough).
For about 1000 USD you will notice how the light transmission, the focusing knob and overall quality is somewhat less impressive. But after reviewing countless of midrange binos I believe the new Swarovski 8x30 CL takes the top spot beating the Zeiss Conquest HD 8x32 in both handling and most of all weight.
Binos at about 500-600 USD is usually where I draw the line. Below this mark the binoculars are difficult to compare as there are so many options and they are good to really bad. But the Nikon Monarch 7 stick out as a surprisingly good pair. They also have the 8x30 version, but since lower quality binos loose light transmission, and the additional weight of the 8x42 isn't so much, I would go with 8x42 version.
Pocket-Binocular My Choice!
I chose the Zeiss 8x25 Victory Pocket as my new primary binocular. It compared well to my old Leitz Trinovid 8x40. It weighs a puny 290 g, a field of view of 7.5° or 130 m at 1000 m, a bright image, quick and near focus, as well as being fog and water proof. The Leica 8x20 was more difficult to adjust for my eyes and has a more narrow field of view. This Zeiss doesn't feel limiting in any aspect except for a bit narrow depth of field. The best binocular for trekking and travels!
If weight and size is the main concern then I would go with the Leica Ultravid 8x20. It has fantastic light transmission for such small binos. The Zeiss 8x20 Victory Compact is less bright and cannot compare to Leica's Ultravid. The Zeiss Terra series binos are bad budget alternatives that I cannot recommend.
Image Stabilized (IS)
They have been around for a long time. Quality and battery life has increased and they can be nice to have on a seabirding trip. Canon has been a leader in this niche, but the angle of view is still a big drawback for birders. Other manufacturers include: Fujinon, Nikon, and Newcon
If cost is of most importance then there are plenty of options areound 100-200 USD. But you must test them out, and try some of the more well known brands. Opticron is just one of many brands. I have not tested this one, but put it up here as one to compare with and what to expect.
I believe monoculars are difficult to use for birding. I have tried out several of them, especially the larger versions from Opticron, but this puny one from Leica has the by far best optics.