Personally, if I considered buying concealable body armor, I would just go without. Negligible protection, expense that could be used towards ammo for training, and in general it’s pretty good at raising your core temp and reducing your body’s ability to cool itself. I wore it for a short amount of time and it was a royal pain in the arse.
Unless you wear it 24/7 you’ll always have to get to where you have it stored to put it on, which likely takes you out of danger and out of the necessity of needing it in the first place. Likewise with a plate carrier. If your job doesn’t facilitate the necessity of it, you likely don’t need it.
However, in the interest of protecting against enemies, foreign and domestic one day, it might be a nice thing to have, and training beforehand will be nice in the extremely slight chance the necessity arises. So at the end of the day I look at it like this: if you already have it, train in it. If you need it for work, train in it. If you could spend that money on ammo for training instead, don’t buy it. If you can’t afford it, don’t buy it. Chances are, you likely won’t need it, and if you want something for more serious stuff, you’ll be better served by owning a legitimate plate carrier.
In the case of the protection against an enemy solder just live long enough to take the armor from a dead enemy solder. This way is risky but you don't have to store the armor and you would likely get the most up to date gear.