Ok, so. The first thing to say, is that I don't really know how to compare their fighting skill. Both aren't really used to fight people of their own level, Gargos has more experience, but Demitri has more recent training, and both are very confident, but Demitri might have learned the lesson after his defeat, while Gargos is always somewhat wary with strangers. Gargos has higher physical range and flight, but Demitri is quite acrobatic.
Gargos is more versatile, with his higher range, the Shadow Lord, one of his artifacts the ability to create portals etc, but Demitri has projectiles, teleportation, shapeshifting, a handy oneshot technique (Midnight Bliss) which would destroy Gargos's body, leaving only his soul to be consumed by Demitri. The latter's huge LS advantage also means Gargos can't use his grabs, while Gargos can only break free through portals.
Gargos should be somewhat immune to Demitri's aura, but his minions are a double-edged blade, since Demitri can eat them too and summon his fiery bats. The stoneskin is also a tricky move, since it has the blatant advantage because of its damage reduction, but the fact is slows his speed makes him more vulnerable to Demitri's dangerous grabs.
All in all both have their tools and advantages, and imho I can't really declare a winner, so I vote Inconclusive.
