um i do not know if you notice but sasori use to punk the crap out of deidara lol that tells you there. but yeah even deidara stated sasori was stronger than him
i think in a way he liked sauske more not trying to be a fanboy, its just he understood him more than anyone in his life, thats why he took it apon himself to train him instead of naruto.
actually itachi was a genuis. he masterd sharingan at 8 and did a full katon fire style jutsu at 6 on his first try. became a anbu captain at 13
but most likely kakashi was a true genius