A person, yes. 9mm is absolutely adequate for defending yourself against people, and even .380 works pretty well. 99% of the time, the correct answer for self-defense is something like a Glock 19, and a lot of time at the range and dry firing.

For hunting mid-sized game (pronghorn through elk) or as a bear defense weapon if you hike in grizzly or kodiak country, bigger is generally better, as long as you can shoot it accurately.

Most modern striker fired semi-autos have no manually operated safety. Using either a semi-auto or a revolver, will require a similar amount of training.

You can do much the same with any double action semi-auto pistol though, or most striker-fired semi-auto pistols. If you, for instance, carry any Glock, or most other striker-fired pistols, you carry in condition 0; the striker is cocked, and there's a round in the chamber. There's a safety on the trigger that help prevent it from being unintentionally fired, but pulling the trigger normally will also disengage the safety. Double action semi-autos are usually carried in condition 2; there's a round in the chamber, but the hammer isn't cocked. As with a revolver, the safety is--usually--the long and heavy pull of the trigger for the first shot. The Beretta 92X RDO has a decocker, but the CZ Shadow 2 Compact has a manual safety; you have to (carefully) let the hammer down on an empty chamber, and then the safety is optional.

You won't find anyone except the most fuddy of fudds that would recommend a revolver for self defense anymore. You won't even find too many people seriously recommending a 1911 as a carry gun (those would be carried in condition 1; a round in the chamber, the hammer back, and the safety on). The only time I would suggest carrying a revolver for self-defense is if you regularly went hiking in grizzly or kodiak bear country, and then I'd be suggesting the largest revolver you could shoot accurately.