The Miami debacle was a textbook example of bureaucratic spin. According to best bureaucratic practices, the FBI leaders had to blame SOMETHING so they hit on blaming the CARTRIDGE (9mm), rather than the PERSON who ordered the felony stop without due consideration of the consequences and appropriate preparation. IMHO, the decision to felony stop at that time was similar to some of the guys we laugh at when they say "hold my beer and watch this..."
The 10mm resulted from the FBI coverup but it was maybe a quick and dirty solution. Once cooler heads prevailed, the 40 S&W appeared. I think it is a much more useful cartridge myself, although I have 2 10mm Colt autos and will not part with them. JMTC, YMMV, ETC.