In ultra short barrels of some pocket deringers the lenght of the .22 Magnum case means that for the same barrel length theres far less bullet travel than with the .22 LR.
For revolvers a short barrel doesn't mean bullet travel will be that much lessened.
I haven't seen any short barreled .22 Magnum autoloaders.
A very loud muzzle blast can be a plus for a self defense handgun. The more noise the better in fact.