>Calorie Mate
I think it really depends on who you believe would attack you. I'd go with AR500 level IIIA because that's going to stop most handheld fun and standard AR and AK ammo. (inb4 AP rounds) If you're worried about military grade rounds, you're kinda screwed. A .308 or 30-06 AP screaming out of a long barrel will punch right through IIIA. I'd accept that it's my time to go if trained snipers are trying to take me out. There is heavier plate available, but my opinion is that once you have to start wearing heavy plate, you're adding a lot of extra weight and sacrificing speed, mobility, energy, and comfort. Learn about cover and concealment. Always find a shelter that makes a good DFP. I hope to run for cover better in lightweight IIIA. That's my reasoning. I'd perceive Jamal and his roaming gang of bandits to be a more likely threat in such a scenario, more than I'd be worried about a military or militia coming after me. One other lesson learned from the desert was Hadji shooting people in the dick, so they made troops start wearing dick plates, neck plates, and it goes on and on. You can plate up till you look like an Iron Man cosplay, but all that defense won't do you any good if you can't move around in it.
One other thing I want to say regarding lightweight armor and placing more value on cover and concealment. I'd invest in hunting gear, especially if you're near a wooded or rural area. Hunting offers clothing for all temperatures and environments. Find a comfy outfit that matches your neck of the woods, and seasonally appropriate. You don't want to wear autumn camo in the spring, obviously. Likewise, if you live in an urban area, walking around downtown in full Mossy Oak will make you stand out like a sore thumb. I'll take as much concealment as I can get. You don't need plates if they can't see you.