But if you reroll for Hanuman, you are 1 additional month behind AND one wind UE event (which means two FLB weapon less). It was already noted when i was writing this reply.
And how high will this base ATK loss be ? 1k, 2k ? And with double upgraded Hanuman you get 80% (40% with old version) additional ele ATK (doesn't matter whether it's 0 LB or FLB). Eidos' on summon effects are another thing though.
Difference with Soul weapon and advantage: 455/375 = ~21% damage gain. Provided you can't hit DEF down cap gain will be negligible. If you can or boss is debuff immune, that's another story.
After buffs those eidolons are on new level of broken.