I think the problem with the most warlike and violent groups have, is that they will eventually eat themselves if they have no one else to make their prey.
This is why I can't imagine a huge empire that simply conquered everything to be really good at science, sociological thinking, or any great technological progress really. It will all just be a collective effort to hurdle their way onto another planet or star and when the maximum inclination is reached. They only have themselves to look at when they want to 'grow' even more.
So in my perspective, peaceful space faring nations should have much better technological progress then violent and aggressive species. Since those types tend to have 'larger borders' but are quite backwards thanks to the 'collective en-masse' type of thinking. Which they put themselves through in order to keep expanding themselves even in the face of different alien races inhibiting them.
This also brings up another point that these aggressive empires really don't value the individuals opinion or thought all that much. And probably inhibit it in order to fulfill the needs of the 'greater good' or 'higher order.'
