The second best handgun is the one in your hand when you need it. The best handgun is the one that fits your hand correctly and is thus more likely to serve its intended purpose when you need it.
Here's a data sheet from a study on handgun ergonomics from a study done by the Federal Law Enforcement Training Center. It's 20 years old, so some of the data may be obsolete, but since the shooter has generally far more influence on accuracy than the gun.....
If I were a firearm manufacturer, I'd be doing this sort of study work on a regular basis and adding data as quickly as I could. Some factors tie in to others in subtle ways. A high bore axis will cause more muzzle flip when you fire and a longer time to get back on to target. OTOH, converting recoil energy into muzzle flip might reduce the felt recoil.
In addition to trigger reach, I'd also consider the mag release reach. Build the basic gun small enough for a small-handed person to comfortably reach both the trigger and the mag release and make available grip overlays to fit the larger hands, and you're broadening your appeal. For newbies, the distance from the middle of the web between your thumb and forefinger to the center of the last joint of your forefinger should be at least equal to the trigger reach listed for any gun you might be considering.
The source for this is Bearing Arms. The actual study, in pdf format, is here.