If one measures barrel length from the back of the casing, I would expect that until one gets to a barrel at least 2" or so long (probably more like 3"-4", or maybe more) the extra distance a .22 short could travel before exiting the barrel would more than make up for the reduced amount of powder. Since the distance from the back of the casing to the muzzle is more relevant to concealability than the distance from the front of the cylinder to the muzzle, it would make sense to compare firearms where the former measurement is the same. And in such comparisons, at short barrel lengths, I would expect the .22 short to win.
I had not thought about it but you are probably right. When both are used in the same gun with a very short barrel, the .22 short travels about twice as far before leaving the barrel.