I decided that I wanted to do a three part series on the advantages/disadvantages of various alignments and would begin with Demon alignment.
Demon alignment has the biggest disadvantage in the game, that disadvantage is being the most popular alignment. This ensures that anybody who decides to choose Demon alignment will have to pay a significant mark up on powerful cards of Demon alignment. Rage of Bahamut rewards Demon alignment has an advantage that made them initially popular.
Demons have the most powerful attack cards with some of the best skills to increase attack power or decrease enemy defenses. There are cards within the Demon realm that do have high defense, but do not compare to either other realm in terms of power. Having the highest attack power out of the realms gives demons the ability to power through the defensive leaders during Holy Wars. It also encourages players to build heavy attack power and accumulate heavy points and rankings during Holy Wars.
The disadvantage here far outweighs the advantage. The game has been progressing and Gods are showing to have only a slight difference in attack capability. They are close enough in attack to note that the difference between the winner and loser will be decided by which card skills activate.
Should somebody manage to have all the best cards available in every slot of their deck for Demon Alignment, that person would be unbeatable. This means that should somebody essentially "beat" the game, Demon Alignment would be shown to be the best alignment. But outside of those circumstances I have never come across a situation where being a specific alignment determined the victor vs which skills activated.