My statement that the best science always wins is of course an approximation. When the levels of science are vastly different, then the much better science will always defeat the lessor science militarily. I was thinking of the British Empire vs Islamic countries when I made that statement.
Consider WWII where the Germans had the better science, at least going into the war, and in my opinion throughout the war. Their initial success came from superior tactics and technology, and the superior technology came from better science than the rest of the world. But the technology was not so much better that it could compensate for the lack of resources in the long run.
In Vietnam, the US lost in spite of having the much better science. So there are exceptions to my postulated rule. Better science is not such an advantage in the jungle.
Regarding who wins what- the British were able to colonize the entire former Islamic Empire. The British won everything, with a limited number of soldiers.
Regarding the Chinese- both sides had equivalent science.
Regarding the USSR- one reason the Berlin Wall came down was their belief that they could not compete with our technology, as exempilfied by Star Wars, and admitted by the last Foreign Minister of the USSR in a lecture at Princeton.
So the Communists did believe in the need for superior science and gave up when they realized they could not achieve it. Of course Star Wars was a bluff, that worked. The Technology demoed in it was ficticious.
Regarding the best science- the best one from the perspective of empires is the won that is best translated into military technology. Right now the US has the best technology. So much so that I fear that the US may becoming a warmongering nation. It will happen if Powell does not exert enough influence. Strange but soldiers in govt are always more like peaceniks than the civilians. Eisenhower is another example.
Regarding the thesis- one could not defend the thesis that the best science always wins--as science and technology is but a major ingredient in the military might of a nation or empire. In ancient times a good case can be made for superior technology and good tactics to compliment it as the basis of the new empire on the block.
But now with nuclear weapons, technology has overshot the mark. Overkill no longer wins. Accuracy seems to rule the day now, which is even more techno based.