The XOR gate concept is astonishingly inelegant. You can build a many-input AND gate out of smaller AND gates. You can build a many-input OR gate out of smaller OR gates. Try it with XOR! This is why I don't build adders with XOR gates except to save space.
I have, as of today, seen a simple implementation of XOR:
https://everycircuit.com/circuit/4934952493514752
It's the only one I've seen. I'm not sure if it's practical, but I'm inclined to give it the benefit of the doubt. It is, however, TTL which is neither fast nor power-efficient.
