I prefer social policies by quite a bit for a number of reasons, but the principle one is that Civ is a strategy game, not a tactical game, and civics encouraged tactical play, whereas social policies encourage strategic planning (which happens to be what I prefer). The civic MO of "what micromanagement can I do right now to get the greatest short-term benefit before I switch to something else for another short-term benefit before finally settling on one thing and then ignoring civics altogether" fits great in a game like StarCraft, which is tactical. But this isn't StarCraft. Social policies encourage - and almost require - you to come up with a strategy and game plan and commit to it. That doesn't mean it locks you into permanent war or nothing but research, but it forces you to think ahead, evaluate your options, and holds you accountable when you chose poorly. Which, in my opinion, is what strategy games should do.
I'm sure some prefer tactical elements in their strategy games, which is fine. But I'm a long-term, big picture kind of guy, and as such I prefer elements that encourage that kind of play.