I've been practically filling my core worlds with commercial zones...
I sorta assumed it was good due to the difficulties caused by long trade routes, which is a hint but not a reason. It looks pretty competitive, though?
Technician: 4 base energy, +25% (5) with Energy Nexus
Clerk: 2 trade value, 2 amenities (some multipliers, but generally less than technicians)
Entertainer: 10 amenities, -1 consumer goods (and a bit more for being specialists. I'm running Academic Privilege which is the worst case, -1 goods instead of -.25). Bonus of 2 unity
For maximizing profit technicians are twice as good as clerks, except that they rely on amenities and energy districts. Looking just at amenities and energy/trade, I guess it's like this:
Technician: 5 income
Clerk: 2 income, supports 1 technician
Entertainer: -2 income (1 goods), supports 9 technicians
In an ideal world (heh) with infinite population and generator districts:
1 entertainer with 9 technicians = 45-2 = 43 profit (and 2 unity)
5 clerks with 5 technicians = 10+25 = 35 profit
So yeah, entertainers are clearly superior for meeting amenity requirements, *and* provide a little unity.
However, I don't think I'll change my strategy much. Spamming commercial zones is much simpler, as it doesn't rely on the natural resources or noticing to add another theater properly. There's "excess" amenities but they're mostly absorbed by the ruler and specialist pops, and provide a nice bonus without going overboard.
Trade goods are also better than straight energy income, since you can assign a portion to consumer goods or even unity. I usually do the first, as it's... simple. Just saves me from making hardly any civilian industries. Which means even less specialists to cater to.
Trade does get much trickier as soon as it requires a route, though. This is just easy for systems with 6 jumps of the capital.
I found a rather funny fast researching build. Just go egalitarian and get utopian and build lots of cities and keep most of your people unemployed. Huge research and unity. Dedicate the rest of the people to growing food and producing consumer goods lol. Just can't do migration treaties because all the unemployed people would rather migrate to the slave empire next door as slaves rather than live in abundance as freelance artists and scientists.
Hehe, I've been wanting to do this since I noticed the research boon. Getting unity from unemployed pops with social welfare was sorta nice, but didn't seem worth doing on purpose. Have you actually tried this yet?
I did have a lot of citizens wander into an empire I didn't realize was fanatic authoritarian slavers... Seems a little odd but it takes all types I guess.