I do go for Planetary Unification. +2 unity is not much but still makes a nice boost while still early. Grabbing outpost influence cost reduction from expansion tree earlier nets you a bit of influence. Then you get the additionnal pop on new colony and +10% growth earlier still from expansion. And the +10% growth campaign you can more easily maintain since you will save on consumer goods by not having clinics, getting a nice surplus you sell for funding the campaign and sponging any deficit, and having more time to set up your civilian industry that should be ready when you will mass deploy clinics.
Instead of getting the same new pop and +10% growth from expansion later, +10% growth from tech, and then additionnal +10% growth from clinics that will be costier on a per planet basis than the campaign. Plus you still can be RNG screwed for clinics if taking Genome Mapping.
I find these additionnal +10% expensive, I prefer delaying a bit of growth while easing the strain on economy and speeding up traditions early. But I play Technocracy and I go Discovery tree second, and I usually get the +1 tech choice perk around the same time I get the +1 tech choice tech, which is rather quickly done when taking Planetary Unification first. RNG has a hard time playing me. For slower tech empires that can be a trickier decision.
