Overall you get most out of the Federalists. The reason is that you can use the 20% economic bonus on your entire economy. This affects your production and research. If you pick, say, Technologists, you get a 20% bonus only on research. Plus, because it's a research bonus, you have to pay for half of the cost anyway! Technologists would have to have more than 40% bonus on research to look even barely competitive with the Federalists.
The same is true for the resources in the game. Always prioritise the economic and military resources. The way you decide between these two, though, would depend on your particular situation.
Difficulties higher than Tough have a hidden, non-shown bonus to research bonuses, whereby at Suicidal you get 2.64x as much bonus research as you normally would. With the 20% from Technologists, this results in an actual bonus of 52(.8)%.
And although you state that you pay for half the bonus, the real treat is in the other half being free. This is still true when factoring in the difficulty bonus modifier, so while you may get 52%, you'll only pay for 26% of it.
Finally, new players to the game have this idea that their economy somehow directly correlates to research and production. This simply isn't the case; without the infrastructure, there's no real difference between an economy of 100BCs a turn or 10000BCs a turn. An economy allows you to build and run an infrastructure, but more experienced players will frequently run negative for up to, in some cases, the first game year. Under such circumstances, it doesn't matter how much money you're making.
With regards to Thorwik's response above, no, the bonus is not transferred, only the base. For instance, if I have 100 MP and am running 50/50 social/military, with a 40% social and a 20% military bonus, I have 60 military and 70 social. If I then set focus to military, my base 50 comes over and gets multiplied by my 20% military bonus, for a grand total of 120 and 0 military and social respectively.
So it is useful to have both bonuses. In my own personal experience, military bonuses are more important than social bonuses, but it does depend on playstyle. For what it's worth, though, military bonuses + Hive needs almost no social.