It might be a bit of bias with regards to how I play sneaking in. I like to rest minimally, maybe once every 2-3 maps if I can get away with it. For context, during my last playthrough I rested a total of 50 times. As a result of that, most of the time if I am playing demon, I get very little benefit from the path as the majority of the power from demonic aspects comes from when I have the rage active, but I cannot rage most of the time due to how I play. In contrast, the Gold Dragon's stat bonuses are up most of the time and so are their increases to spell dice, as well as their immunities. Demonic Rage is not comparable to spell slots either, since you can very easily extend angel spells to 24h and get their full benefit across an entire zone, even when you do not rest often.
I also do not rank mythic paths according to what they can do at level 20 mythic rank 10, but rather according to how they play within whichever portion of the game is available to them. Demon and Aeon consistently lag behind other paths for the majority of the game. Any build you make on a demon (with some minor exceptions with regards to kineticist) could be better done on another path. Whilst Aeon is for the most part similar, its edicts do have some niche use and in "burst" scenarios similar to where you would use rage powers, in my opinion provide more utility.