For speed of access in a carry gun, I like the Express Sights. For target shooting I use a medium to wide undercut front profile. I find most adjustable rear sights are a bit too narrow in the notch, however, and that I have to file them out wider and re-finish them. Perhaps by now someone has come out with adjustable rear leaves, like German air pistol sights? That would be ideal.
Small sights once dominated target shooting on the premise that a tight sight was needed to keep tight alignment and to track a small point of aim on the target. I have a pre-war K-frame .22 S&W my Great Aunt bought new for $38 during the depression. I inhereted it in the original red box, with only six rounds ever having been put through it and the originally purchased box of copper-case Remington cartridges and the factory instructions and sales slip still there. Probably should have mothballed it as a collector's item, but was young and proceeded to shoot it. It is a long-stroke DA that is as smooth as glass, has a factroy installed McGivern dot on the front sight, and a tiny little continuously adjustable rear sight blade. Terrible to try to see through clearly. I don't know what McGivern got out of that arrangement, but he sure seemed to make it work? In more recent decades, experimentation, mostly by Russian and European coaches, has shown that tiny sights cause eye strain and extra tension in the shooter. They also encourage the tendency to jerk the trigger attempting to "ambush" the ten ring when alignment is momentarily perfect.
I prefer all soot-black for bull's eye targets, since the tagboard provides plenty of contrrast. Bo-mar is traditional, but requires frame milling. There are new designs that don't. Colored lines, blade ramps and dots may be useful for nearly invisible targets, but even then I find them a distraction in all but low light. I hate white and flourescent orange outlines. They never seem to give me the same vertical alignment the actual sight profiles do. Not sure why? Individual focus issue, maybe? Tritium is useful in very low light.
Nick