[necovek]

I would say that the US/EU plugs which are symmetric are more resilient than AU plug: with AU plug, an electrician can connect wires the wrong way, yet with EU/US plug there is no wrong way: devices handle either polarity because the sockets and plugs are symmetric.

US plug has a drawback that there could be a live connection with exposed prongs, similar to two pronged EU plugs: both apply with flat sockets (eg. you may touch the exposed pins).