Conquest

They mimic the Faction Bonuses that enemies in Conquest get, so if you get the GR tech, then you can field a GR squad that reflects damage the same way as the most annoying Padmé squad of all time. They only last for "X" number of victories, though (and I think X=2 but don't quote me).

I can't remember the specifics of FO & Resistance, but they can help you get a couple victories against nastier opponents that you wouldn't have been able to get otherwise, especially if. your faction is underdeveloped.

But honestly, except for Steadfast Retribution there's always a GL that can get through any node you need to get through, and everyone on Hard should have 1-2 GLs, minimum.

I mean, it's nice to get them for a faction you like or need, sure, but the rest of us do without just fine.