- Banker:
3%/turn passive income is hypothetically interesting, but also that's just 300/turn extra income at 10K funds, so it's hard to get a meaningful result out of it on most missions. - Entrepreneur:
On one hand, you're definitely going to have a Community Center (or a few) and this creates a situation where you can earn money by disabling production.
On other hand, each person working at a (lv≥2) Greenhouse produces ~1.5 food/turn, and food usually sells for at least 30/piece, so doing so isn't such a good deal. - Comedian
A slight morale bonus (+0.25) can push you over to the next per-citizen income level when colony size bonus is 1.9 or 0.9, for example. - Musician
Same deal. - Architect
Getting a full metal/glass refund is pretty good if you expand towards a resource deposit without building much of anything else on the way there. Not so useful for exploration/terraforming since you don't get electronics back. - Geologist
Getting 3 terratech per recycled resource and faster terraforming makes Ground Stabilizer actually somewhat usable. - Recruiter
"More options" means that you always have an option to accept 5 more colonists than you're supposed to be able to at most. Usually default maximum is already tricky enough to keep up with unless you want to accept colonists every other time instead. - Logistician
The exact benefit of this specialist is a little hard to measure since you can't tell which trades you wouldn't have had otherwise. - Botanist
Kind of neat - lets bacteria evolve with 3 neighbors instead of 4 and you can get a spice/turn out of a fungi-tile with two nearby stalagmites by placing an extra fungi tile next to it instead of making a third stalagmite. - Engineer
Life cycle part means that "topping up" a deposit with a terraform now adds not 20 cycles, but 22.
Development bonus is neat - now you need 1 and 3 depots instead of 2 and 4 for level 2 and level 3, respectively. - Hydrologist
Picking a Hydrologist unlocks turbo condensers (which cost 12 glass instead of 10 glass and yield 3 water/turn instead of 2) and marks random water tiles underground (not all of them though). The latter part is great - not only you now have some pointers for where to dig for water, but also where you might dig in general. - Speleologist
Knowing where hidden passages are is a pretty big deal, especially on the surface. Speleologist can make a big difference on underground-centered missions in general. - Scientist
This is a big-brain specialist, in more than one sense.
Picking a scientist generates a new selection of specialists, but it also makes you more likely encounter your desired specialist, whomever that is - if you have noticed, the game never offers the same specialist twice, and you get to pick specialists three times, so the odds of you encountering any given specialist are 9/13. But if you've picked Scientist, the odds are now 12/13.