Well whats great about several of the major companies is the selection of weapons they offer that follow the same platform. Sig, S&W, Glock, most 1911s offer several versions, calibers, and sizes but use the same platform.
Training with any of these weapons are very easy and can be done with most all the models because of that feature. Being in law enforcement the majority of my handgun training goes with Glock models 22, 23 and 27 which are the same gun in a different sizes. The training only differs in carry method.
It is great if you can carry one weapon all the time and have it suit any need that might arise but it is more practical in the Military than as a civilian or civilian law enforcement.
"We must reject the idea that every time a law's broken, society is guilty rather than the lawbreaker. It is time to restore the American perception that each individual is accountable for his/her actions." -Ronald Reagan-