Kesshi is right. Plains are food-neutral when farmed and thus cost a pop to basically give 1 hammer.
Now, evaluate what you're going to grow onto with that 2 food, if the best tile you can work right now is just a plains tile. The answer is more plains, or something even worse. In a PURE hammer city with food surplus that doesn't have the techs needed to make things like workshops viable, plains farms are good whip holdover if you can't work anything else and are waiting for
to cool, if the city has that kind of surplus food and is already working all of its hills.
Otherwise, the specialist provides more actual output now (food is not a direct contribution unless building workers/settlers, food is potential that only gets returned later via whips or additional worked tiles). Usually 3 yield of SOMETHING (4 if you go with a spy and can steal tech) is stronger than 1
now and a marginal tile later.
If the gpp produced will actually generate a great person at some point, the value is *much* greater.
At biology you can do much better with the 3
1
tiles. Under state property + caste a city with 20 plains tiles only can run 10 farms + 10 shops and hit 61 base
...pretty good. Of course, it's still weaker than grassland with 20 tiles under caste (you can work all workshops and put up 80 base
), but suddenly it's very usable. Likely you won't run pop 20 in a production city, but you see what I mean now. They're weak tiles no matter how you slice it, they just become usable about halfway into the tech tree or so.