More often than not, both ends of the spectrum are exaggerated in one way or another.
One side makes the argument that the right bullet is like a Star Trek phaser, the wrong bullet, is like a cork gun, the bad guys can't hit the broad-side of a barn from the inside and the good guys are masters of Ninjitsu and James Bond mixed with Neo.
The truth is that most modern defensive bullets perform about the same from any cailber/cartridge, the Bad Guy is likely to be using something similar, no bullet guarantees instant incapacitation without a CNS hit, the Good Guy is likely to miss a lot, and the BG will miss too, except he might not miss, and the GG isn't Neo or James Bond and (s)he's likely to get shot too.
While many bullet wounds are not fatal like a phaser, they do have a way of massively disrupting your plans. A hit in the arm, for instance, isn't going to blow your arm off (whether it's a 45acp or a .25acp) but either of those (or most anything else) does have an EXCELLENT probability of rendering that arms nearly or totally useless.
Expect to get hurt.
Expect to hurt back.
Never give up until the light fades.
Still happily answering to the call-sign Peetza.
You do not HAVE a soul. You ARE a soul. You HAVE a body.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.