My best friend and I were in his truck after grabbing a bite and he asks me, "So, what should I get; 9mm or 45?"
I asked him, "Well, depends on what you are getting it for?"
He then replies, "I want it for CCW."
This led into a long discussion on whether this was to be a weapon he actually carried or one that stayed in his night table. Eventually, he got frustrated with my questions ans just asked me "Why can't you just tell me which one to get? What's so hard about that question?"
I shrugged and looked at him, "There is no right answer. It's a personal choice over which fits you better for your needed purpose. I was asking you questions only you can answer and allowing you to pick what works for you. There is no right answer. It's a compromise."
I went on to explain that a 9mm pistol tends to hold more rounds then a 45 and is often smaller, lighter, and can be thinner..making it a little easier to conceal. A 45acp is generally agreed to have more stopping power, at the cost of a thicker, heavier, and slightly more difficult weapon to conceal. Also, a 45 acp weapon in a sub-compact size would probably not be all that pleasant to practice with, while the 9 mm would be less bruising in a tiny package.
I did steer him away from a full fized weapon, like a Glock 19 and similar ilk and lead him to something a little more easily concealable. In the end he decided to go for the ultimate compromise cartridge, thr 40 S&W....almost the capacity of a 9mm with almost the stopping power of a 45 ACP in a 9 mm package.
Now comes the tough part...and fun part...to the rental range !