Yes, because they're meant to kill - of course they're a better deterrent than something not meant to kill...
The numbers you quote, which came from actual studies, are valuable; however, the rather important contrast (you left out for some reason) is that given the average annual defensive firearm incidents reported - the number of violent crimes committed using firearms is astronomically higher (in 1992 for example, 931,000.)
Statistics clearly state that gun ownership is not an effective deterrent to violent crime committed with a gun.
I'm not interested in taking peoples' guns away, but it does get annoying to listen to the bullshit spouted in the name of "guns are good" and "the only cure for a bad guy with a gun is a good guy with a gun" types of stupidity.
BTW, not sure where you got the crazy numbers of 2.5 million and 4.7 million given that in 1992 there were fewer than 4.7 million violent crimes of any time (robbery, murder, manslaughter, rape, aggravated assault, et cetera...)