Is there a point in saving more civilians in XCOM 2?

Solution 1:

There is an achievement¹:

Heroes of the Resistance

Beat a Retaliation mission with less than 3 civilian deaths.

Otherwise, as long as you manage to save at least 6, I couldn't identify any difference in the outcome. There are no rewards for Retaliation missions, so there's no difference there.

You are offered a cache of supplies/intel/materials by the Resistance after completing a Retaliation mission, and it's possible that differs based on how many civilians you save, but if it does, I couldn't detect it at all. I also looked through the XCOM 2 source released with the mod tools, and there doesn't appear to be any different treatment for Retaliation missions compared to any other type.

_{1: According to skully, the achievement unlocks from less than 4 civilian deaths, in contradiction to its text. I was also able to confirm this in the XCOM 2 source.}

Solution 2:

Saving 6 civilians yields an additional contact gained as an award. Saving eight yields two additional contacts.

So far I generally finish clearing out all opposition before saving ten, but I'll try and check sometime if that has any additional effect.