I prefer the 9mm or the 45. I carry a .40 cal as a police officer, and it just so happens it is an M&P. The .40 is a popular caliber, that is widely used all over the country. I simply prefer the .45 for its larger wound it causes. But if you dont care about that sort of thing, the 9mm is the best choice. It is the most used caliber world wide, and therefore can be bought in military surplus. Also keep in mind that the .40 is a 10 millimeter bullet. It does not make much bigger a wound chanel than the 9. All that said, the guns you mentioned are for duty/personal defense. If shooting enjoyment, recoil, and cost of ammo are concerns, buy a 22 target pistol. Ruger in my opinion make the best. They are cheap, and last 10 lifetimes. I own several auto loaders as well as revolvers. I have the most fun with Ruger .22cal. A nice compromise is to buy a 1911 type .45. The ammo, like 9mm is available in military surplus, and you could later get a .22 cal conversion kit for about $200. This is a great combo. You shoot .22 for practice, and fun, then change over to .45 for carry/ home protection. To get cheep ammo, try going online to Cheeper Than Dirt, or The Sportsmans Guide, to name 2 of many. I have purchased .45 for as little as 40 cents per round, new production, by Wolf; 9mm at half that price. Military surpluss may be less, but not by much. I hope this helps. Oh and by the way, the Smith is a pretty cool gun too.