I see one difference....training with thousands of rounds of .22lr is far more economically feasible than using thousands of rounds of centerfire ammo. Less wear & tear on your carry gun, too.
Especially when you are training rookies and the department doesn't furnish training ammo. It took some convincing but eventually I had all my regulars shooting 22's, some pistol some revolver and it didn't make a lick of difference. A few sessions with their duty gun over the course and when it came time to qualify they all scored high and one just missed high score for the department by 1 point. The man who beat him was the chief deputy and former trainer and he got his extra point with a head shot.
Good intentions will always be pleaded for any assumption of power. The Constitution was made to guard the people against the dangers of good intentions. There are men in all ages who mean to govern will, but they mean to govern. They promise to be good masters, but they mean to be masters.