Your premise is that less training time and money can be spent if we go back to revolvers for primary carry by LEO's.
No, that is not my premise at all. My premise is that if typical LE went back to 6-shot K-frame model 10s with .38 Spl. +P ammo I don't think there would be any significant change in the gunfighting effectiveness of LE. Saving time and money would be an additional benefit, but that is secondary to the main issue, IMO.