User blog comment:FairyRaven/Fairy Tail Chapter 435 & 436: The Cry of Victory & Memoirs, Review and Commentary/@comment-24039234-20150518203351/@comment-7418318-20150518224209

The Etherias were made out of pure magical energy, while the Homunculi were made out of souls of dead people. I think that's quite a fundamental difference.

In a way the Homunculi of FMAB were Necromancy if you will, while the Zeref Demons are their own kind of magic.