[jen20]

A non-exhaustive list:

- fused in the plug

- longer earth pin opens the live terminals to prevent accidental or inadvertent insertion into the live or neutral parts of the socket

- sockets are usually switched which avoids sparks when plugging in

[JAlexoid]

They're an over engineering person's wet dream.

They have multiple safety features that stem from ancient wiring systems used in UK, but they aren't inherently "better".

They don't even deliver more power, for the bulkiness of them.