Mathematically, it's pretty easy to prove (and I'll be happy to elaborate) that between the researchers that affect multiple generators, Crit Power > Production >> Crit Chance. At rank 9, Crit Chance is a little better for you since you have so little of it, but I would only upgrade it when it's cheap. Comparing these to commons is pretty simple, but requires a little math.

Comrade and Discount researchers are a little harder to compare, but the consensus among higher-ranked players is that Comrades are the top priority and Discount is worth roughly as much as Production.