Kenneth Woods argues that Haydn was a more creative, more talented and more skilled composer than Mozart.
My first reaction was that this was insane. After reading his article, I now think that given what Woods means by this claim, it may well be right. But I also think that what he means by those words is an eccentric thing to mean by them. What he goes on to say about Haydn and Mozart seems to me to advance the claim that a) each of them was better in some respects than the other, and b) the respects in which Mozart was better are more profound. Any version of the claim that Haydn was a more creative, more talented and more skilled composer than Mozart thats consistent with (a) and (b) strikes me as a pretty watered-down version.
Still, definitely worth a read.