Ivan, the Swaro 25s are small and lightweight. They will fit in a large pocket and weigh ~350g. 32s and 42s are much larger and heavier. I assume you will use them in conjunction with photography gear? If so, get the 8x; it will give you a bigger picture and you'll be able to find birds more easily. Then, you can get a closer, image-stabilized, look with your camera and a 400-600 lens, which are the equivalent of 8X and 12X binoculars. I have owned a pair of 8X20 Zeiss pocket binoculars for over 10 years. I use them mainly when riding a bicycle. Since I progressed into photography subsequent to becoming a birder, I have Zeiss 8x42s and Swaro 8x32s, which I can use all day with minimal strain. Pocket binoculars are better for occasional use. Zeiss has since replaced the 8x20 with 8x25, which you might want to compare with the equivalent Swaros.