I'm not sure the US isn't imperialist by your definition.
At the very least the second Iraqi war hints to the contrary. It appears the main agenda there was a grab for oil and not a security threat.
Not to mention its behavior in South America during the cold war.
Now, I prefer the US over China, because its ideals are at least against imperialism and pro human rights, democracy and freedom. They might not always do what they preach, but these ideals combined with soft power approach, is (was?) A source of good.
(If only they didn't hate socialism so much, and didn't prefer corporation freedom over human freedom, it would have been even better... well, let's hope the EU can survive)