Between the 21 and 25 I can see how it would be hard to say which is technically better. I can't speak for the 21 yet (probably my next lens) but every image has been jaw-dropping that I've seen. I can say the 25 is definitely awesome by any measure. Even Zeiss is proud of it, and it broke some records. It was my default lens on the M8 (because of the near 35mm equivalency).
So if the consensus is that the 21 is as good as the 25... Good! That's quite a compliment.