An excerpt from Wikipedia; there’s more if you want to look it up. There’s plenty of other articles if you don’t care for Wikipedia. Bottom line, nobody, perhaps except yourself, cares for the 9mm as their duty handgun. If they’re carrying it, it’s because they’re required to.
By the early 1990s, most M1911A1s had been replaced by the M9, though a limited number remain in use by special units. The United States Marine Corps in particular were noted for continuing the use of M1911 pistols for selected personnel in MEU(SOC) and reconnaissance units (though the USMC also purchased over 50,000 M9 handguns). For its part, the United States Special Operations Command (USSOCOM) issued a requirement for a .45 ACP handgun (Offensive Handgun Weapon System (OHWS) trials). This resulted in the Heckler & Koch OHWS becoming the MK23 Mod 0 Offensive Handgun Weapon System (beating a Colt OHWS, a much modified M1911). Dissatisfaction with the Beretta M9’s stopping power has actually promoted re-adoption of handguns based on the M1911 design (along with other handguns) among USSOCOM units in recent years, though the M9 remains predominant both within SOCOM and in the US military in general.
[edit] Current users
Military and law enforcement organizations in the United States and other countries continue to use (often modified) M1911A1 pistols including Marine Force Recon, Los Angeles Police Department S.W.A.T. and L.A.P.D. S.I.S., the FBI Hostage Rescue Team, F.B.I. regional S.W.A.T. teams, and 1st Special Forces Operational Detachment—Delta (Delta Force). The Tacoma, Washington Police Department made history in 2001 by becoming the first metropolitan police department in nearly 50 years to adopt the M1911 as its official carry weapon.[8] The Tacoma Police Department selected the Kimber Pro Carry II or Pro Carry II HD as optional, department supplied weapons available to its officers.[8]