You are spot on in the fact that there are always trade offs.
Yeah, and thats the reason many of us own so much different glass.....it would be hard to have 2 instruments that would work for everything. Are you really going to want 12x binos on a Whitetail or run and gun Elk hunt?
Heck, I like to have the option of carrying 8x and/or 10x on hunts. When I'm moving a lot I find I use the 8x a bunch. I like sitting behind 15x binos on a tripod in open country and its usually enough for me....but then can see why a spotter is a necessity for some. Its so dependent on what and how you hunt....when hunting the west, its nice to have choices.
If I was limited to ONLY 2 pieces of glass; for me and the hunts I do it would probably be the 8x and 15x binos