By the way, do any of you go communist for the low corruption benefits? I know it's great for warmongering, but I found it really nice for having a large peaceful empire too.
You can have a large empire with republic too, just don't build any structures in your corrupt cities.
In conquest, a scientist specialist gives 3 beakers per turn.
Assume 21 grass tiles:
A single communist metropolis: size 20 city all tiles with road, rail, and mine.
This city produces 21 base commerce, you can expect it to have about 20% corruption, but lest assume a rosy outlook and assume 10% corruption: that leaves 18.9 commerce after corruption.
This city will have a courthouse (1gpt) police station (2gpt) aquaduct (1gp) hospital (2gpt) market (1gpt) bank (1gpt) library (1gpt) university (2gpt). totaling 11gpt upkeep. (assuming you have all 8 luxes and don't need cathedrals)
And in modern times it will also have a factory (3gpt) recycling (2gp) mass transit (2gpt) Stock Exchange (3gpt) totaling 21gpt upkeep (I will assume you have hover dam, and the internet.)
To pay for its own upkeep you'll need to run 50% tax. base tax will then be 18.9*0.5= 9.45 and with the market/bank/SE this will become 23gpt income. and 2gpt will go to your stash.
you'll have 9.45 left over for science, the improvements make it 23 beakers per turn.
The shield output of this city will be 21 from mines, 21 from rails, 2 from the center (metro bonus) =44 shields, with the same rosy 10% corruption, that makes 39 shields. with a factory and hover, this becomes 78 shields. Good for pumping units, but you are not warring...
Lets say you build wealth, with economics tech, this will become 39 gpt.
you can now set the science slider to 100% your city will now output
47 beakers per turn, and
18 gpt left after upkeep.
but you can only do this after you complete building all the improvements.
The city can also
support 6 units for free.
The city will also need to gather 6*20+6*40+12*80=1320 food before reaching its max size.
Now lets look at a republic, if these 21 tiles are in a corrupt area, you'd build 7 towns very close to each other, all tiles with road, rail, and irrigation.
Each town will have 2 citizens working, and 3 scientist. Each town is producing 1 commerce per turn, 1 shield become 1gpt with wealth. support 1 unit for free, and 9 beakers from the 3 scientist.
In total,
63 beakers per turn,
7 free units,
7 gpt from wealth, and 7 commerce that could be added to either tax-income or science.
Each city will need to gather only 100 food to reach its max size.
And you will need to give them very little attention once set up.
Conclusion: The communist set up is only useful for pumping out units.
For 100K culture games, (where you want to use pop-rushing) you'd use feudalism in conquest, as its not an optional tech.