It's their weight that propels the coins
The difference being?(not trying to be offensive here I'm not entirely sure what you mean)
Rudimentary firearms and Plate co-existed, it wasn't until later that plate was forsaken in lieu of armor designed for bullets, and I would argue that even bullets aren't enough to crack plate
hammers and maces best use is blunt force trauma, namely against the head , breaking armor is something you see in movies but wouldn't happen under normal circumstances,