Breakthrough! There are essentially only 3 variants of the Devilman manga:
Probably identical to how it was published in magazines. The scanlations online are based on this version (specifically the 1972 one), except the "Great War of the Gods" and "Sirene" colour chapters included in some uploads, like the Mangafox one.
The 1993 version is an almost identical reprint of the 1972 version. The easiest noticeable difference is Kodansha's logo in the top-left corner of the front being written with kanji instead of the latin alphabet.
- 1972, 1978, 1983, 1993, 2000 (3 volumes), 2004
- 1987, 1997, 2000 (omnibus), 2002-2003 (Bilingual), 2008, 2009 ("Refurbished edition")
Appear to be close to the Deluxe editions except for the visual touch-ups I mentioned before. I have also heard it include content from Neo Devilman; I'm assuming it's the fifth story.