Good question, I think just metal does this on its own and there are videos out there to substantiate that, as I have seen this on other blogs. However this does not take into account all factors, such as bullet trajectory or a plate inside of a vest. Dependent on many factors I would assume anything is plausible.
I don't know if you have seen field testing on Dragon Skin, but it is amazing, however there is a weak spot in that if the impact is from a low enough angle, its useless.
At any rate, if I were looking for something inexpensive and had the ability to guard my heart, lungs, and all other vitals in the torso, I think I'm going with something similar.
just my humble opinion.