The correct answer is that it depends on your perceived or likely threat.
If you are carrying 9mm for an expected use against unarmored humans, a "Self Defense" hollow point is a good idea. Lots of the folks I know up in AK, and me when I lived there would carry heavily for caliber ball or solid ammo in the woods becasue we were looking for penetration in moose or bear, but not stepping up to a rifle. My dad carried a .45 w/ JHP for years in anchorage, but kept a magazine with ball in his truck in case he came across (or was in) a traffic accident that injured a moose and he had to put it down. (talk about a low probability event to plan for)
The old saying that "mission drives gear" applies to a self defense handgun in spades.
To Perd's actual question I don't think much good data exists. For every one of us that thinks about the proper cartridge for the threat and use, there's someone as was mentioned that just wanted the cheapest ammo for the gun. There's probably (literally) millions of handguns in peoples closets and nightstands that are loaded with whatever the gun store sold the person when they bought the gun, because they are on the first box of ammo. Those are a mixed bag of what the gun store flunkie thought was good, what was in vogue at the time (.38 spl wadcutter!!), or what was in stock at the time.
for myself, I carry whatever brand name JHP had the best price the last time I bought 500 of them. Right now, that's a mix of 124 gr Federal Hydrashock and 124gr Speer Gold Dot in 9mm or 230gr Speer Gold Dot +P in 45. At any given time there's probably a couple mags of range ammo in the truck too.
