There is a fourth case: Complicated.
Short version: Write lefty, throw righty, and shoot some guns better lefty, and other guns better righty.
I do some things better right-handed, and some things better left-handed, but do almost no task equally skillfully, with each hand. I write, use a fork, and do some other fine motor skills left-handed. I tend to use a knife, or similar tool, in the forward grip, better right-handed, but often switch to lefty for reverse grip, which is not just for fighting arts, but mundane knife chores, too. A pushing motion is something I will tend to do right-handed, whereas I may well perform a pulling motion left-handed. If I want to shoot a Glock accurately, I’d better shoot lefty, but I generally shoot a long-stroke double-action handgun right-handed, largely because I learned to shoot DA revolvers after I had decided to carry on my right hip, instead of my left. DA revolver shooting may be the closest thing to my being an “ambidextrous” shooter. Single Action revolvers are something that I do slightly better left-handed.
Shooting a single-action firearm is something that I may perform better left-handed, at least on some days, especially if slow-fire. Drawing a pistol, especially a heavy pistol, is something that feels more “natural” if done right-handed, but that could be simply due to more draw-and-fire training reps being done right-handed. So, in a draw-and-fire setting, I am going to perform more efficiently right-handed. I have mostly used 1911 pistols that did not have ambidextrous safety levers, so, most of my training reps with a 1911 have been right-handed, but, there have been times that my targets shot lefty, with a 1911, have shown smaller groups. I am not quite ready to declare that I am a lefty, with the 1911.
I throw right-handed, which would prompt some scientists to declare that I am right-handed, because throwing is a whole-body motion, which some schools of thought will say really and truly shows how the brain is hard-wired. Drawing the then-mandated heavy duty revolver, from the then-mandated low-slung duty holster, was not unlike throwing underhanded, which was a factor in my choosing to carry on the right side, in 1983/1984. Texas did not yet have a handgun licensing system, at the time, so carry was not “a thing” for me, until I was hired by a PD, in 1983.
I am left-eye-dominant, which may well be a factor that helps my lefty shooting, regardless of motor skill level.
I took piano lessons, at an early age, and later played a clarinet, while in the junior high school band. (Not my first choice of band instrument, but my parents were frugal, and so I used a handed-down instrument.) Many musical instruments require that both hands do important things. Both the piano and clarinet require that each hand play an equivalent role.
So, I could make a case for being lefty, or righty, or, ambidextrous.
