Mew are tied.
In the first movie, Mewtwo claimed that the clones were superior. He attempted to prove their superiority and worthiness by defeating the non-clones in battle and then allowing his storm to wipe out the rest of the world.
And Mew's role was a direct parallel to this (although this wasn't made very clear in the dub). Mew claimed that the clones were inferior and were not worthy of living, so he engaged in battle with Mewtwo to prove his own superiority.
In the end, neither of them was able to defeat the other. And if Ash didn't step in, one of them may have eventually killed the other... but out of pure luck. They were completely evenly matched -- neither was more powerful than the other.