Here's my $.02:
The best defense against a bullet is DON'T BE WHERE THE BULLET'S TRAVELING TO!
That said...
It's all about Protection vs Movement. You could be all done up like a MW3 Juggernaut and still die. How?
1. Armor makes you slower to varying degrees, the heavier/thicker the more cumbersome the armor. The slower and less agile you are, the more vulnerable a target you offer. It will make you winded quicker and again the goal is NOT to get shot in the first place.
2. Impact. The purpose of armor is to keep the bullet from penetrating the protected portion of the body. The bulk of the energy from the bullet is dissipated along the area of the armor "plate". However, some (varying on caliber and level of protection) energy is still transferred through the armor to the individual. At best you get knocked off your feet, winded and have a little bruising. At worst, you can expect broken bones (which can puncture organs and lead to) as well as internal bleeding. During a situation where medical care is with the civil war ERA and modern hospital settings are out of immediate reach death will still be likely unless proper care can be given. (I'm not a doc, just going off what I know.)
You have to ask your self if it is worth the cost to you at this point. As MountainRedneck so eloquently pointed out, you can't eat SAPI plates. If you have the extra scratch to spend 300-400 buck on a good set of plates, go for it.
At most I will be running Level 3A soft armor (currently) and even then it will be mission specific. This is because my goal is to stay light and mobile, able to move quickly and use that extra weight for ammo. If I was to wear armor, it would most likely be for a "door to door" situation, which I do not see myself doing anytime soon, or in a defensive situation.
Also, be aware of what you are buying. Make sure you are getting the appropriate level of protection you want. Also note the date of manufacture of the armor. Most body armor has an expiration of about 5 years. This is a manufacturers warranty thing so I could see them being effective "to a degree" for some time past that date. Also be aware that there are such things as "training" plates on the market that offer no protection but give you the weight and bulk of armor. Bottom line on this subject is research, research, research! And Buyer Be Aware!
Proper care and maintenance of armor is also key to its effectiveness. Hard armor must be periodically inspected for cracks, dings or other anomalies which could lead to a catastrophic failure of the armor at that most critical of moments. Its must also be kept clean to preserve the integrity of the materials it is made of. Soft armor is no different in the regards to cleaning and inspection. I also recommend that you store your soft armor laid out flat. The reason is that when storing for long periods of time, over time the material has a tendency to "sag" and collect in the bottom of the carrier. This reduces the surface covered by armor and creates unnecessary bulk. Regular care and maintenance can be the difference between your armor doing its job, or failing when you need it most.
