Our group is gearing up our WHM with Determination, for overall more increased healing, to help with the AoE Healing, which is his job in our group.
But since this is about Materia, I say try to go with as much MIND the gear can handle, and fill out the rest with Determination.

For me, being the Scholar in my group, will go with Crit, to get those really crazy shields up on the tank.