There is no straight forward answer... The closest I can give you is this: If your agency is not issuing you one or specifying what you should get... Ask/find out what ammunition will be issued to you. I presume they will specify a caliber. Rent 2-3 firearms (or more if you have choices and time) and run at least 100 rounds of the specified ammo through each. The firearm I would recommend is the one that: 1) runs the spec ammo the best, 2) is the one that you will practice with, and 3) the one that will carry the best in a holster. This advice has nothing to do with Bob's Gun with the exception that they do have a good selection of rental handgun in the major calibers (but they may not have the ammo that your agency issues, and they require you to buy their ammo if you rent)
You need to talk to the company you are working for, but more likely it would be a 9mm.
I would say the company you work for. Would tell you what you can carry. Bob's would not be able to give you a straight answer. Due to legal reasons
Thanks! Your answer is awaiting moderation.