Something I've really come to appreciate in ME1 is how all three Council members are consistently and coherently characterized during what little interactions we have with them, and especially how they are different shades of pragmatism.
Now this is interesting because when you delineate characters through foil dynamics, you usually give them contrasting traits : a pragmatic character would be contrasted with an idealistic one. Yet since we're talking politicians, idealism is unlikely. What do we get instead ?
Valern's pragmatism is very much all about short-term efficiency : getting the mission done is the only thing that counts. Results are the only things that counts. He's a textbook example of what a cynical pragmatist might be depicted as ; which is perhaps why Esheel, in a Renegade!Timeline ME3, seems to have nothing but contempt for him.
Sparatus' pragmatism, on the other hand, always manifests itself as caution. Did you take this in consideration ? Do you have proof to back up what you claim ? Can you stop being a maverick for two seconds ? Can you conclusively demonstrate to me that you took every other possibility into account and that you did, in fact, make the best available decision ? It's pragmatism but focused on the long term, on not jeopardizing the future for the sake of the present. Strategy instead of tactics.
And as for Tevos, she usually has the last word, always mediating the reactions of her co-Councilors and the Council's responses as a whole. The feeling you get is that her pragmatism is all about flexibility and compromise : what's done is done, what's most important is that we agree on a mutually beneficial course of action. She juggles egos, unruffles feathers and calms everyone down so that they can move forward.
This is very nice because, in a sense, each of them is a perfect vanilla representation of their respective governments, in keeping with ME1's heavy worldbuilding duties : Tevos is very much the compromising centrist asari are supposed to be, favoring people working together (at practically any cost) over what they're working for ; Valern is all about the short-term mentality of the salarians, and the certainty any problem they cause can be fixed no matter what, in a never-ending parade of problems whose resolution cause other problems ; and Sparatus is risk-averse and perhaps the most conservative of the three, in that he is very afraid of any significant change upsetting the status quo, always calculating how this or that decision might change the grand strategic stage of the galaxy.
