Late game your pops have huge bonuses to FIDSI. If you want production and science late game, what you really want are population slots. That typically means terraformed worlds.

There area few types of world below Terran to consider - Boreal is both fertile and cold, allowing for large amounts of science. Desert is maybe, maybe, better for production. But Jungle has more slots and is fertile, as well as being hot.

I like the idea that Riftborn are the only faction that strive to have sterile planets.

It stands to reason that other factions would go for fertile planets.

I understand the logic that if you are able to terraform a planet you should be able to do it both ways but I can accept the choice to make it separate as a gameplay limitation for balancing.

Dreepa wrote:

But going from ice to arctic had the preview of changes show -8 science. You sure that the 1 extra pop would make up for that?

What you always benefit from is going from Barren / Ice / Arctic / Snow / Tundra to Boreal.

Ice to Arctic conversion is good on any planet size except huge.

Going from Ice to Arctic is a -4 in science (from 12 to 8). On a huge planet that also means going from 6 to 7 population.

On a large planet it is going from 5 to 6.

On a medium planet it is going from 4 to 5.

That 1 extra population is producing 20 science (8 base production, +4 from planet specialization for science on cold, +2 from Punctuated Evolution Fundation, +1 from Magnetic Field Generators, +3 from  Graviton-shielded Laboratories, +2 from Microwave pipes)

There can be anomalies or hero skills that increase this value further (like additional +2 from Magnetic Field Generators if planet has anomalies).

You could also cound +1 from Power of the Endless but I won't count it here is that is endless tech.

On a huge planet you lose 6 * 4 = 24 science from that terraforming action.

On a large planet you lose 5 * 4 = 20 science from that terraforming action.

On a medium planet you lose 4 * 4 = 16 science from that terraforming action.

So you can say that on large you have the same science output but output on other FIDSI increases and happiness also improves so it is worth it.