First off, in non-combat situations, armor has limited value unless it's concealed. (you just shoot for the head or abdomen.)
Plate carriers are good for military and SWAT team use only.
I've worn level 3 and 3A, without plates) for an entire watch, and it's miserable. Heavy, hard to conceal, and hotter than hell.
Level 3 will stop handgun bullets including .44 magnum. Level 2 will stop 95 percent of handgun rounds, and is the choice of many older, experienced officers. These are Kevlar.
Plate vests, that will defeat .223 and .308 are Kevlar with steel or ceramic plates, in pockets . They can weigh 25 lbs of more, and are impossible to conceal.
Good "tests" of body armor. if it costs less than about $750 (or more) new, pass on it. The good stuff isn't cheap. If you can't conceal it under a loose fitting shirt, pass on it.
If you're not military or LE, stay out of areas where you might need it.