Thu Aug 08, 2013 8:19 pm by Ryeballs
Elemental disadvantage affects an attack of a certain monster against the element of a certain monster. Underdog removes the attacking disadvantage.
So basically:
Iajutsu: 58x2 power
Super Thunderstorm: 120 power plus STAB
Mind Bending: 90 power using lower MATK vs lower MDEF
Iajutsu will always lose out, even compared to regular Thunderstorm, the negated Elemental Disadvantage from Underdog and the fact that Iajutsu doesn't get STAB.
Mind Bending will only be better if the disparity between MATK and MDEF is waaaaaaaay bigger than the disparity between ATK and DEF, which probably isn't the case. You can test this out using Electric Ball and Mind Game (both beginner moves or 10 EoW) against any level Minotaur since those moves have pretty much a 4:3 power ratio, the same ratio between 120 Power STS and 90 power Mind Bending.
Frankly, if its close at all, use Aurora over Mind Bending though, because against plant it will do more damage if its not Raining making you more effective against Plant too and strong MATK enemies are fewer and further between.