You sir, appear to have an axe to grind.
I stated that "Plains farms are almost useless until Biology. Most of the other plains improvements are better."
I have no axe to grind just a different opinion and one that's backed up by maths. You've made two statements there and they're both wrong. That's why I called them nonsense, they don't make sense, and can't make sense the way you stated them.
In spite of what several people have stated here, a plains farm is often quite useful. Any tile that is food neutral and can give a hammer is useful in the right circumstances to those who know how to use it. People that say otherwise are, put frankly, ignorant. Of course it is a mediocre tile and sometimes a weak improvement but that is not the same thing as useless or almost useless. A competant player trying to get the most out of what he's been given should try to make the best use of all the tiles he controls. That means using the weak tiles as well as the good ones. Any fool can use the best tiles but the best players squeeze a bit more out of the weak tiles and don't ignore them when there is nothing better to use.
We're discussing the 'Best Tile Improvement for Plain.' Cottages qualify as an improvement.
I know and I make due allowance for plains cottages.
But I only build them in cities where I need commerce and not more generally like I would a farm. A plains farm (pre-Biology) is only useful for production and so is not directly comparable to a cottage, they're different things used in different ways. Which is what I said originally.
A plains workshop on the otherhand is only used for production and so it makes sense to compare that to the plains farm since they are rival improvements. I did that and for most of the early and middle game the plains workshop is a much weaker improvement than the plains farm.
Metal Casting, Machinery, Guilds, and Caste System are all available earlier than Biology, so workshops, windmills, and watermills start to become viable candidates earlier in the game.
Before Chemistry a plains workshop is at best the equivalent of a plains hill giving 0F4H and since it takes 2 food the net output is much reduced by the value of the food. That food has to be supplied by other tiles and has other uses. To get even that weak output you have to run Caste System. Very often that is a weak civic that early in the game. I know there are some powerful strategies using Caste System early in the game but they work better on higher difficulties (Emperor and above) when lightbulbing key techs is a way to compete. Running Caste System just to boost early workshops is hard to justify.
Losing Slavery to gain Caste System is a major weakness of the workshops approach. As many as 50% of my cities at that stage will have surplus food but no tiles for workshops and they lose the production potential of Slavery. In those cities I would be forced to run sub optimal specialists that don't have Rep, produce no useful GPPs and don't have infrastructure to boost the specialist's output.
In contrast, a plains farm produces 2F1H so that is food neutral and does not depend on any civics for its output. It is much the best production improvement for a plains tile since it is more flexible and in small cities is more efficient.
Workshops only really become competitive when you have Chemistry and State Property and enough cities with workshops to justify running Caste System as well. In a CE running US gold can be used as a substitute for food to boost production in cities without workshops. In a SE running Rep and Caste System only hammer tiles plus engineer and priest specialists provide hammers.
Well you do carry on about this, so you must be onto something.
I don't have a firm grasp on this aspect so I'll look more carefully at what you wrote about the hammer yields with respect to city size.
You should look into city size
, it's one of the most important aspects of the game when understanding how cities work. You need to think about big powerful cities with many good tiles in a different way from little cities with a few mediocre tiles like plains. They need a different form of management in terms of infrastructure they build and also different tile improvements. The big cities are where you can produce loads of commerce or GPPs and where national wonders go to boost output. It is worth investing in a load of expensive infrastucture buildings including happiness and health. Little junk cities build a minimum of infrastructure and pump out a steady stream of units, by means of whipping, drafting and hammers. Generally farms work well in the small cities and workshops are more useful in large cities where whipping is less efficient.
I can argue as well that those EP will contribute to the EP spending modifier that also grows with time ( as long as you generate more EP ). Not mentioning that I am already throwing out the GPP ,as you requested 
The comparison I made is the only undiscussible one possible ( just in game ratios ), and that is why I used it.
I think of him more as a Greek rather than a Buddhist. The Delphic oracle to be specific, giving obscure prophecies that the user interprets any way he chooses. The two adjectives I'd apply to Dave are laconic and enigmatic (both great greek words 
as does a plains wood. At size 10 a plains farm has the same productivity as a plains hill. At size 20 the grassland farm and plains farm have the same productivity in terms of food-hammers. They are far from useless, you don't know how to take proper account of their worth, if you think that.
for less population, so i have a choice whether to run a specialist or work a cottaged tile/mine/whathaveyou.
I always thought it only affected universal suffrage rushbuying.
