Here is my take on bigger apertures. There may be slight optical advantages but they are NOT worth carrying a big binocular for. I once had a Fujinon 7x50 fmtr-sx and Swarovski Habicht 8x30 W at the same time. Comparing them under different lighting conditions I couldn't believe how LITTLE difference there was between them. I also tried Henry's Zeiss 8x56 FL and compared it to some of my other alpha level 32mm and 42mm binoculars. Take my word for it. It is NOT worth carrying a 56mm binocular birding for a better view of the bird if you are walking or hiking. If you are in a stand where you are not hiking much you might use a bigger aperture. For birding stick with a 30, 32 or 42mm binocular. You are not going to miss much by not carrying a 50mm or 56mm binocular and your back and arms will be a lot happier. I use my Canon 10x42 IS-L when I am not hiking a lot because it has IS.
I generally agree!
I've had a 10X32, 10X42, and 10X50 SV. For general birding I don't think most can tell the difference, it's hard for me to.