Hits on the target is what I use as a rule of thumb. I'd rather have a hit with a .22 than a miss with a 9mm. As has been stated, there are a lot of variables when matching a person to a firearm. The term "light recoil" could mean the shooter is inexperienced, has health issues that relates to using a handgun proficiently, or other reasons (noise) to be fearful of a firearm.
The term "easy to use" could mean different things to different people. A revolver is easy to use. Just open the cylinder, load, close the cylinder and your ready. With a pistol you load the magazine, insert the magazine into the pistol, and chamber around by sending the slide home. While this sequence is easy, for the inexperienced shooter it may not be.
Generally 9mm is regarded as the minimum for self-defense. Try different handguns/caliber combinations to whittle down a preference to buy. Check out .380 caliber pistols that are offered as easy to manipulate. I think S&W has come out with some in .380 and I think 9mm as well, though not sure about the 9.
Whatever you decide on, practice. Know how the firearm works. Over time safe handling of the firearm will become second nature.