It's come to my attention lately that a lot of folks are advocating shooting for the head when attacked by somebody that they suspect are wearing body armor. Bad idea. For one thing, this is going to guarantee your death because you're probably going to miss.
Everybody seems to forget that in this case your adrenaline is going to be raging through your veins like Niagra Falls, your motor skills are going to go to shit when you're in a stressful situation and most of us, myself included, do not have the intense training necessary to overcome those facts.
Shoot for the chest. Body armor is designed to absorb and halt the penetration of the bullet, not the shock and force associated with a bullet strike. If you shoot somebody at point blank range with a 45 ACP, he's going to get hit with 500-600 foot pounds of energy and it's going to stagger them back. We've all seen dashboard videos of LEO getting hit with a gunshot in their body armor and not a one of them was able to simply shrug off the strike and immediately return fire. It either knocks them down or forces them to take a couple of steps back.
Shoot for center mass, then quickly adjust your point of aim and eliminate your threat.