No matter what one pet is going to be preferred in fights that actually matter because all the pets are is an extension of the Summoner's damage - Ifrit has a stun but that's not Summoner's job (And it comes with all the woes of being melee), Titan can tank, but that's not a Summoner's job. Nobody cares if Ifrit is marginally better than Garuda in trash clearing or if Titan can help you solo overworld mobs because clearing content like that is basically assured regardless of what you do.

The pet that is best at optimizing DPS in Coil-esque fights is that one that will be summoned, the rest will be ignored.