You have to keep in mind that: summon I = ranged dps (caster type), summon II = tank, summon III = melee dps - after 50 the best to use is summon I, because having Garuda-egi on obey maximizes your dmg as summoner, you chose when she uses specific spells to help you out AND she dies less then ifrit-egi who takes the blasts from boss because being a melee dps.