For example if you plan to uses potion to recast a Flare quickly ether or hi ether is better due to cooldown you can use more often.
Just a correction: Ethers and Hi ethers do not give enough mp return from 0 to cast flare.

But I do always keep lots of HQ mega etheron my BLM for this purpose. They offer the lowest recast (at 3m 36 sec) on a recovery item that gives enough MP to cast flare from 0.

Always nice to add another free flare to your rotation. And the recast is pretty close to being up for the beginning of both pulls for an average Brayflox 2 boss myth farm group.