OK, I'm not touting any great experience or superior ability on my part, but I've been using binoculars for nearly 50 years. I probably have 40 different ones to my name now and have cycled more than that. I'm not trying to disagree or agree with any post on the thread.
This is just my own personal perspective in favor of 8x. There are several things and one event in particular that really have helped in shaping that perspective. The event was an optical display (maker irrelevant) at the local big deal "Bald Eagle Conference". This outfit was in the process of introducing a 7x42 and 10x42 binocular model. They had results of their work into the decision in favor of 7x over 8x. They also had a series of different magnifications of this same binocular in 7x, 8x, 9x, and 10x. They had a relatively simple test protocol that they had the mostly quite skeptical audience was asked to fill out. As it happened, when they presented their local results at a last day of the show workshop, the local results paralleled the rest of the research. In short, some 70% selected the 7x. about 20% the 8x and about 10% selected the 10x. This was from starting out not knowing what they had. The unmarked binocular just had a test sample number on it. That outfit sold a PILE of 7x42 binoculars at that show. Predictably, the 7x did not last because consumers not aware of the research just assumed the 7x was too weak and opted for the 10x. Everybody thinks the extra 1x gain of an 8x will show more detail, and the 20% increase of the 10x over the just has to be better still. What everybody thinks rules the world I guess.
I'm not going to detail the times I could ID something with an 8x when my partner and his 10x could not. I do not doubt for a nano second that guys with a 7x could not identify what they could with 10x either.
I have a bunch of 7x binoculars and I doubt that much more than 10% of viewers could tell they were 7x and not 8x. I'd venture that those who can are defined by the percentage of the participants who selected 10x from the series of magnifications in the blind test. I've done this some on an informal basis and your average user sure can't tell.
Here is some food for thought with 8x, and why I tend to favor them. Yeah 10x is 20% larger than 8x. Since that is the case your eyes are working harder to process the extra magnification. As magnification increases, depth of focus decreases. Quite a bit between 8x and 10x. So for me I like not having to run the focus as much with 8x vs 10x. I prefer a view with a lot of area in front of and behind whatever buck I'm looking at that is in focus. Image shake has been mentioned, but that is a personal deal. Some shake worse that others. Shake for me is not an issue. Magnification also tends to magnify heat wave distortion. There have been times I was glad to have a 7x that would show something where the 10x had too much mirage effect to be useful, in my experience anyway YMMV.
The short story is either one works. That is why the argument exists. The preference of one magnification over the other is a personal preference. I have given up trying to convince anybody to chose one magnification over another. The reason for that is that, in my estimation, the way the binocular fits your face and in particular your eyes, particularly with regard to eye cup shape and eye relief is a hell of a lot more important than whether or not you are gaining or losing anything with a 10x vs and 8x. Contrast and color balance also come in ahead of magnification. So does how the binocular balances. Kinda like a good rifle. Do you want a 30-06 that fits like a glove or a 300 Wby that you have to fiddle with to get behind? Or a rifle scope with an eye box that suits you vs one that doesn't?
So, to the original post, as far as either an 8x or a 10x, like I said, both work. Pick one and go use it. I personally have never felt I have lost anything with an 8x. You are the only one who can decide that and you may have to go through some different ones to figure this out
