i dislike both, but i would have to say western imperialism, due to the fact that they have a lot more blood on their hands and they kill so many innocent people around the world (especially the Middle East). they also twist and corrupt peoples perceptions of other groups of people.
Plus there is a lot of things we do not know about, about the American Government and the CIA. just a few weeks ago they came out with the fact that they were involved in the 1953 ousting of the Iranian President, just because he wanted to renationalize oil. I reckon they do a lot more then they own up to, which is why i respect Bradley Mannings, for reveling some of the lies of a nation that only cares for power and the influence it has over the world.
I also dislike that both governments (the UK and the US) think they're the best thing since sliced bread.