As far as numbers of fish, I catch most of em while brookie fishing, and a size 12 Parachute Adams is my go-to. That's also pretty typical for the March Brown hatch (nymph and/or dry), which I fish as much as any other. Add to it that most of my egg imitations are on a size 12 hook, which is the go-to for steelies, stocky rainbows, and occasionally wild browns during the sucker spawning season. So I'll say 12.
It's fairly rare that I fish anything bigger than that, though. I do, on occasion with say, streamers, drakes, etc. But those are fairly rare.
Whereas 14's and 16's are pretty common at sulpher time, 18's are common at BWO time, and I use 26's for midges and trikes every year.