Are you kidding, 2/3 farms? Using your assumption of no plains you don't need a single farm (although you might want one to accelerate growth). I generally have 1-3 farms for a size 20 city while running a cottage economy. With flood plains you can cover every tile with cottages.
Read the sentence preceding that quote:
Lets say we want to match the food gain while using b).
It is a starting point to assume that food production should be equal otherwise we are comparing two totally different quantities and need to come up with a fair conversion rate between food and commerce. Also, looking at the wikipedia, with Currency, a freshly built cottage is going to take 24 normal turns to catch up in total commerce production to a freshly built Aristocratic farm. In the meantime, that farm was producing an extra food or two over the cottage, so the city is growing faster, or is supporting a specialist, or is supporting a mine to get commerce boosting infrastructure in faster etc.
I generally have 1-3 farms for a size 20 city while running a cottage economy. With flood plains you can cover every tile with cottages.
If you have 2 farms in your size 20 city and convert to Aristocracy and run one more farm instead of a 5 commerce town you get just as much food, and actually gain 1 commerce. If you have 3 farms and end up having to run 5 farms under Aristocracy to feed the population you end up gaining 1 food total and breaking even on commerce. And thats assuming that every other tile in your city is a Currency powered town. If you had underdeveloped cottages you are coming out even better. If you are financial you are coming out significantly better and breaking even even on commerce if you were only running one farm before and had to upgrade to two. This is actually a flaw of my earlier argument when I said that Financial helped cottage/farm and Aristocratic farm equally when it very clearly helps the Aristocratic farms more.
One drawback of Aristocracy is that you lose some flexibility in city specialization. It becomes harder to settle a hilly area and make it into a production monster since you are losing a food in those critical farms. But the upside is you get to take maximal advantage of Agriculture, all your cities are pretty much self sufficient very quickly. Later in the game, if you transition to a specialist economy with the advent of Scholarship, it is almost seamless as you have the farms in place already. You are working great tiles to take advantage of Slavery and Drafting.
Now let me talk about God King, because I really believe this is an overrated civic and it keeps getting brought up as a huge opportunity cost of being in Aristocracy. High Upkeep plus increased distance maintenance means that a large spread out civ is going to be hit hard in the upkeep department by moving from City States or Aristocracy to God King. "That's Ok, I just run God King when I'm a more compact civ". Fine then, how valuable is that 50%
gold bonus in the Capital? Answer (at least in my experience with non Khazad civs) = not very since in the smaller empire, you will typically be running a high research slider and thus will not be taking very much advantage of it. The 50% production bonus is nice and if you are wonder-grabbing it is possibly a lifesaver. But if you are running a different government civic and are able to afford a larger empire, the presence of more cities should mitigate that production bonus almost entirely. I still do not understand why it isn't getting the full Bureaucracy bonus which would make it as good as everyone seems to think it is.
There is also the issue of getting aristocracy without cottages if you don't have gold.
I never said don't build cottages, by all means cottage up those plains while you are working on the techs you need. What really helps is the presence of City States early in the tech tree on the way to keep your economy afloat while you rex and develop the infrastructure/improvements/trade network needed to get your tech rate up. But agreed, getting the techs necessary to have the Aristocracy available and effective is the most painful part.
