The plates are capable of being much more effective than the soft armor.
Currently we employ Interceptor Body Armor, or IBA. This is the "soft" armor, or "flak jacket" that is standard issue. It has been upgraded several times over the years. I think it has a IIIA rating, which means it does pretty good against pistol and submachine gun rounds, and small fragmentation, but isn't going to do much to stop a high velocity rifle round, be it Commie crap or not.
The vest has pockets to allow hard ceramic-steel plates to be inserted in the front, back, and sides. These are called Small Arms Protection Inserts (SAPI). I think they are rated Level IV, which rates them to stop certain rifle rounds. There is also a thicker Enhanced-SAPI (E-SAPI) plates which offer increased protection against multiple rifle rounds and armor piercing ammunition.
I've seen an E-SAPI with two M118LR rounds (175 gr HPBT Match sniper round for the 7.62x51 NATO), four standard 7.62x39 ball rounds from an AK, and five M855 ball rounds from an M16A4 all on the same plate and not a single one penetrated. And my brother had a team leader in the Army that took seven rounds (count em!) to the back SAPI as he was coming into a room on point his first tour and didn't even realize he'd been hit until someone pointed it out to him after the engagement. Not one round made it through. Obviously, the plates are capable of offering decent protection. However, they are bulky and heavy. With just the front and back plates, the IBA will weigh around 30 pounds IIRC, and that's without the CamelBak, IFAK, mags and ammo, knives, batteries, and other junk the soldier or Marine is expected to hump around.