Why do some have skull with wings vs regular head with wings?

Belated reply is belated.~

I think it's just the difference between winged skuls and winged angels.
Which is, itself, indicative of a difference in cultural attitudes towards death.

Tldr: As religious trends moved away from Puritanism in the 1740s, and the idea of "salvation" became more accepted as a given, it became more acceptable to put angels on stones instead of skulls.

And that's the -short- version. :P