Pistol dilemma, 9mm vs 40S&W vs 45ACP?

I'm about to graduate college and go into law enforcement and I am about to buy my first pistol. I have shot and held several pistols and have one in mind I am leaning toward purchasing but I'm not so sure about the caliber. I know law enforcement mainly uses .40 and .45 but I would probably use this gun as either a concealed carry or home defense pistol as I would probably be issued a pistol by my employer or instructed on what to get. Either way, should I go with the 9mm since it will be my first pistol to get comfortable with it or should I get a .40 to be comfortable with the pistol I will use in my line of work? If i should get the larger caliber, is the .40 or the .45 better in terms of handling/recoil, I'm not necessarily concerned with stopping power and badassness.