Pierce is my favourite, because Morningstar, bitches.
No seriously, pierce is good because if you get cut (except abdulla great o mighty) your hits will only tickle tincans , then they will itch you. Or If you get a blunt weapon, a ninja(a skilled one) will come and kill you before you can even swing,and tell you what you wont knockdown anyone after the latest patch, so If you go with pierce, you will have enough damage to open tincans, and significant speed against fast guys, also pierce glances less than the other two , from what I see.