Eh, in the end, they are both made for different tanking purposes.

Gladiators excel at tanking a single, heavy hitting target. Paladin will expand on this even more.
Marauders excel at tanking groups of less damaging enemies. Warrior will expand on this even more.

I think Gladiator is more efficient at reducing damage and keeping the focus of a single mob. On the flip side, I think Marauder's AoE damage is better suited to keeping groups of enemies on them.

When it comes to Ifrit, I would prefer a Gladiator. For an EXP party, a Marauder would probably be better.

Apples and Oranges.