Yeah, this is a big misconception. I'm a huge .45acp fan through and through, but if I shoot a guy in the head with one of my .45's is he gonna be any more dead than with even a .17mach2? Of coarse not. Also, it's simple physics, if what you fired from your handgun didn't knock YOU down when you fired it, it's not going to pick your enemy up off his feet either when he get's hit by it. That being said though, a heavier bullet traveling a nearly the same velocity as a lighter one has the POTENTIAL (not garaunteed) to deliver more kenetic energy to it's target. Resulting damage is all about the actual bullet, ie; hollow point, fmj, flat lead tip, solid lead, blah blah blah. Crappy ammo can leave a lot to be desired in any caliber.
True, and it all comes down to a personal preference. I enjoy 9mm and .40 cal ammo. I have owned a .45 but I am a 180lbs and in very good shape. I refer back to my military/Law enforcement caliber because I am confident if I wake up to an intruder and im tired I can easily deliver 3-6 rounds very rapidly and accurate. With out a doubt I can head to the range and throw down some .45 like no ones business, but having consideration for neighbors and their property I chose a glock 22 for my EDC