As Overkill mentioned... If you want honest answers, peruse this site. If you want a lot of snarky answers, stick with yet another thread.
Caliber choice lies solely on the shooter. Fortunately, I can shoot a multitude of calibers comfortably; therefore, I keep five calibers laying around (still "need" more). My uncle shoots 9 mm almost exclusively, because he prefers 9 mm. Shoot what you like. As long as you load a good name brand defense ammo you don't have anything to worry about.