Revolvers ARE pistols. In fact the term, pre-dates autoloaders...
The term pistol goes all the way back to the 16th Century. The origins of the word are uncertain...but the term pistol was in use before revolvers were invented, and certainly before semi-automatic pistols.
Most people today do split the handgun category into two subsets: revolvers and pistols. Actually that isn't exact, since there are single shot handguns (example: Thompson Center Contender) or double barrel, single shot handguns (example: derringer) which are neither revolvers or pistols (if you accept that designation.)
As for my choice of only one handgun...it would have to depend on the reason WHY. If it was the end of the world, then I'd opt for a 4" .357 Mag...either a S&W Model 27, 28, or pre-lock 686, or a Ruger GP100. Ammo is common, a number of configurations are available (.38 and .357, in various weights and bullet shapes.) These guns are unlikely to need springs or other parts, and don't need magazines.
If it was just personal preference, that I only wanted to have one handgun, and only one, then it'd be a 5" 1911 in .45 ACP. It would be one with no FPS, and one that has a lifetime warranty from a company that has excellent customer service: Ruger SR1911, Springfield Loaded, or S&W "E" series.