I'll echo what's been said already. I can physically hold the 12's decent, but for one handing while archery hunting and just general increased brightness and field of view nothing beats a good pair of 10's. Personally I'm a fan of the 10x50's in lieu of the 10x42's, but that's just me. You can tripod mount any bino and run them and immediately extend their range, but you can't make higher power binos easier to hand hold.
On another note, you'd be excited how far you can realistically glass and spot and even judge animals with 10's. My buddy runs 10x56's and I run 10x50's and we were on a mule deer hunt for him and glassed up deer at about 1200 yards, and were able to judge the 4 point he ended up taking easily enough to know he was a shooter. The only thing higher power would've done would be resolve the 2" cheater he had on his right side on the back fork on the inside. That took the spotter. But otherwise, we could tell he was a 24" 4 point with eyeguards. 12's wouldn't have given us the edge in judging the cheater, 15's might have, but what really did it was the spotting scope. My suggestion is a good quality pair of 10's, a solid tripod, and SLOW DOWN while glassing. You'd be surprise how effective the 10's will be!
Agree with the comments above in that this depends on the individual. With that said, based on what I’ve seen on this forum, it appears most/all handhold 10x and lower. Some handhold 12x, and a very limited number of individuals regularly handhold 15x and up. Zero science behind that statement, but that’s the impression I have after years on this forum reading optics threads.
I use 12X as my regular carry bino's and take the trade off of less stability for the extra power at long range off a tripod, but if you are using them without ever intending on using a tripod i would recommend 10X due to movement causing more distortion at longer ranges with the increased optical zoom.
I can use 12s just fine free handed with no issue...until I get the shakes too bad or something I will never look through a pair of 10s again.
That being said by dad uses Swaro 8x as he can not hold anything higher magnification steady enough. I agree with most that 10x is probably the betting mans mag for steady holding.
I am on the other side of this situation. I use 8 (now 8.5) x binos because I can't hold a 10x steady enough. I have tried many times, and with really good glass, but I just can't do it. But I sure can see better in my 8.5s (My 9x45 Mavens were really good too, but was right on the edge). So...for me, I can't reliably use a 10x with out a tripod. Just like others have said, it really depends on you. I notice my shakiness easily at 10x. 12x is a "must tripod" situation for me. My 15x are still a great tool, but always with a tripod.
I will say though, that I have never been in a situation where a 10x would have made any real difference for me than my 9x Mavens or now my 8.5x ELs. I see every bit as much if not more than my buddies with their 10-11x glass. We hunt big basins of the Intermountain West and use our tripods a lot.
I’ve been using 12x50 EL for 3 years. If you’re walking in the mountains and throw them up quick to check an animal you can see great but if you really need to glass for some time you need a tripod to get the most out of them. After using these for 3years I really can’t see me using anything else. Before these I was using 8.5x42 EL for over 10 years but like these a lot more.
I’ve been through so many binos due to too many hobbies. Boating with 7x Steiny’s, wildlife photography with 10x42s… mistakenly took those on an Antarctica photography cruise (high seas made it tough to hold still), enjoying landscape views across Lake Champlain with 15x56s, etc.
I have yet to put any on a tripod. Although, I have never hunted out West.
The reason for this post is to say I have noticed preference changes from year to year. Last year I was primarily using my 15x’s. This year I’m quite satisfied with 8x. Before it was 10x.
The luxury of having a few pairs is something people rarely discuss on these forums.