Kind of depends on what you're doing, but here's one consideration - if you're planning to keep it in a vehicle or somewhere it might get tossed around, consider getting steel plates. Yes, they're heavier but they won't crack under abuse like ceramic will and they're considerably cheaper. I've got multi-hit-rated IV ceramic plates but keep meaning to pick up a set of steel plates for different applications.    BTW, always keep in mind that you may need to ditch your armor in a hurry. Current-issue PASGT vests and Blackhawk STRIKE carriers have quick disconnects which can let you drop all your gear fast. So fast, in fact, that you could sprint into a building wearing armor and a trenchcoat or duster, pop off your gear, and walk back out unarmed and let 'em keep looking for the armored combatant while you casually stroll away from the scene.