should i do imps or stormcloak for my dark elf assassin i killed the emperor already i killed all the merchants in whiterun lol

Go read the "Great War" then the "Bear of Markarth"

Then you can decide.

I would also recommend talking to the people involved in the latter.(They paint a much different picture than that book)

But also talk to the leaders and lieutenants of both sides.

Whatever floats your boat.
Any race could do well for both sides, IMO.

I have thishttp://betweencontent.com/article-the-skyrim-civil-war-a-look-different-sides/, where I go over most arguments for and against each side. A couple of things should be known before you read it though: I am no longer in favor of the Empire, as I state in that article, and we now know Morrowind is not a part of the Empire anymore.

Stormcloak.