Not positive but I suspect the non-military facilities like Power plants do not use "staff" in the same way that the military ones do (Barracks, Fabrication plants, sea piers, etc.). The Personnel will be employed from you citizens I suspect so unless you want to keep unemployment higher (which one may in fact want to do) I wouldn't guess the personnel is that much of a consideration.
I haven't played the game much and certainly haven't done the maths, which I tend to think would be very context-dependent for the simple reason that: not all regions are equally positioned to acquire the resources needed to construct and run all the power plants. These kinds of 'opportunity costs' would be difficult to quanitify I'd say.
The rule of thumb I follow is: long-term try to fill out all hydro slots that are available. Yes they are expensive to build (about 10x petrol power for example) but as far as I can see neither petrol or hydro 'cost' maintenance in SRCW (thought they did in SR2020). After you have a hydro built that is basically free permanent electricity, so if you can afford to initiate the building of one I say 'why not?'
I would say the same thing about most of the other 'resource free' ones: once you can build them, if you have the fiscal/industrial goods ability to get building why not? If I could get all of my hydro slots filled I'd happily deactivate all the petros or coals or nukes that I could.
If you have no hydro hexes but you do have coal then go for coal; if you have no coal then go for petro; if no petro then I guess the question of 'which one is best' really boils down to either (a) which non-resource type can you get to fastest in terms of techs or (b) which resource commodity is likely for your region to acquire cheaply in the long-run? The answer to that (b) might seem to be a simple economic question about market fluctuations in coal, oil, uranium . . . But if you are in a position to quickly conquer a neighbor who has tons of uranium then I'd say it is once again, more of a strategic costs analysis and not a simple economic one.