great post, thank you, your experience helped me a lot, at this moment i am deciding whether or not to get the 15x50 IS, seems better not.
regards
It depends what you want to use them for. I've had both. The 10x42 are wonderful optically, but if you want to use them as "all-round" general purpose binos, beware of the chunkiness and weight. They have the ergonomics of a toaster and the weight of a brick. I traded mine.
The 15x50 might not be as good optically (they don't have the L-series glass), and they are not fully waterproof. They are easier to hold than the 10x42. I kept mine, and use them sometimes as a "scope-substitute" when I don't feel like carrying a scope on a long walk. Over long distance views like marshes and estuaries, they are lighter and easier to handle than regular binos plus scope. I also use them for seawatching, when my eyes get tired of scoping. 15x will never be an "all-purpose" bino, though. For this I prefer 8x.
However, the Canon IS 8x25 was presumably designed by an alien engineer who had never seen human eyes or hands, and who scoured the universe for the cheapest, tackiest plastic from which to construct binoculars, inserting into them the most useless, jumpy IS-system his deluded extra-terrestrial mind could conjure up. I have a pair. I gave them to my brother. He gave them back. I'm not sure if burying them on a moonless night with a stake through their IS-system will rid my mind of their horror.
I think if I were to rewind a few years, I would get the 12x36. These are probably the most versatile, and surprisingly comfortable in my hands. I had a pair but dropped them, thereby discovering another limitation of Canon IS binoculars - they are well-nigh impossible to repair, no matter how many times you send them back.