dansiegel30, you will note that I did not dispute that research and economic projects are not generally worthwhile, and in fact said that I agreed with that sentiment. You will note that what I took exception to is the demonstrably false claim that the use of economic and research projects is strictly inferior to directing planetary production into the desired output types.
The statement "I tried it on a planet where I had ALL Manufacturing (and yes Marigold, an approval building, as well as some farms), and I tried to see which was better, to put population points into Research or Economy, or use my awesome manufacturing capability with the Research Project or Economic Stimulus. In all attempts, using population points won! In every possible way." constitutes a claim that, under what are essentially the most favorable conditions for the use of projects, the use of economic and research projects is strictly inferior under any performance metric to directing all planetary production into the desired output type. In other words, you made the claim that there are no conditions under which you will see a net benefit to using a research or economic project as opposed to simply directing production into the desired output. Worse, this is the only support you provided in the original post for your claim that economic and research projects are not worthwhile. This is a demonstrably false statement, and it is the only support you provided for your case.
I thought they just gave a 10% bonus through being 'on', regardless of the amount of industry you put into it.
No, they don't. It isn't communicated that well within the game, but the bonus granted by the project is equal to
0.1 * ceil(m * s * (1 + M) * P / 10)
where m is the fraction of planetary production put towards manufacturing, s is the fraction of manufacturing allocated to social production, M is the planet's manufacturing bonus, P is the planet's production, and ceil(X) is the function which returns the smallest nonnegative integer N such that N >= X. You can see this in game by looking at the tool tip for the output type corresponding to the project; 0% manufacturing means that the project doesn't show up, while social manufacturing in the interval (0, 10] gives a bonus of 10%, social manufacturing in the interval (10, 20] gives a bonus of 20%, and so on.
The net bonus of an economic or research project is less than this, of course, being
P - m * (1 + B + P)
where m is the fraction of the planet's production given over to manufacturing instead of the desired output type, B is the planet's bonus to the output type corresponding to the project, and P is the bonus you expect to see from the project.