Magnification can be both your friend and your enemy. It seems to be universally held that more of anything is better than less. I agree sometimes more is better. Magnification does the obvious, it increases the size of the image we see. It also magnifies everything else you can think of too. Next to the image, the next most obvious thing is the magnification of movement. Most obvious are muscle tremors, either from being tired or from not having the steadiest hold desirable. As the shake starts, so does our effort to counter it. That just makes things worse. Breathing and pulse rate factor in here too. The stars typically align for best handheld use in the 7-10x range. You are better off, in my opinion with lesser magnification that can be held steady. Some can use more than 10x. I can handle 12x for a while, but without a tripod, I'm just fooling myself at 15x. After muscle shake, the next most obvious is magnification of heat waves. On a recent hotter than hell Beatty's Butte Antelope hunt with my nephew, the mirage was so bad that I was glad I had thrown in a couple of 7x binoculars. They were usable. The 10x were just a blur. Increasing magnification also reduces the depth of the field that is in focus.
I would venture the opinion that you probably will not enjoy the 15x freehand. Somebody said they doubted you would see a lot of difference with trhe 15x vs the 12x. I tend to agree with that view. Personally if I can't get the view I need at 8 or 10x, then 20x is about where I need to be. I dislike spotters, so I'm considering 18x and a tripod. It is also my opinion that focus quality is at least as important as optical quality at 15x and up. You can jump through a narrower depth of focus pretty quick with a tight, or too fast, or sloppy focus. At any rate I agree that with 15x, a tripod is a must have. A good tripod. Don't skimp on the tripod.
