wouldn't cloud have materia at his disposal? if so cloud ftw easy. if not dante but, it would be an awesome and relatively close fight.
i look at it this way...
cloud has his limit breaks. dante has his devil form. dante wins in that regaurd. i think dante is more durable and could withstand an omnislash and could come back to unleash on cloud.
physically both are equal in terms of strength.
in combat i think dante is one of the best there is. cloud, even as good as he is, is his lesser in this regaurd.
noctrune is cannon. it was also made by namco. if u look at dante's feats in nocturne maniacs. then ull know that almost nothing short of a megaversal power can truly bring dante down. cloud, awesome as he is has no chance in hell, materia or not.
capcom never made nocturn. atlus did. dante was added in with permission from capcom. namco has nothing to do with that.
as for it being canon, I don't know.
dante never even dt'd in that game. I guess you can fit it in the story, seeing that dante went there after dmc2 and going to hell, meaning he never even tried hard(reason there was no dt).
dante in sparda form showed more megaverse power, whatever that is supposed to be.