I'm not sure the two are directly comparable beyond the little guy won. Yuan Shao lost becuase he had, perhaps being senile, had lost his edge whereas Cao Cao was still at his peak at Chi Bi. Yuan Shao lost becuase his camp was badly divided, whereas Cao Cao doesn't seem to have such internal trouble, Yuan Shao lost becuase momentum stalled, he got hit with key defections, Yuan Shao's best commander (Qu Yi) died before hand, key defeats demoralised them and then supplies got destroyed by a daring strike from Cao Cao. Maybe the momentum one and one early defeat counts for Chi Bi.
One of Cao Cao's strengths was his willingness to take a gamble with a sudden attack that might otherwise have been inadvisable. It worked for him at the last at Guan Du, where he so very nearly lost, against the Wuhuan and yes, taking Jing. Not surprising that he followed a usually successful formula against a wavering Wu and a potentially demoralised Liu Bei to see what would happen, it was a gamble but one that might have worked. Remember Wu was divided as to how to react to Cao Cao and could easily have allowed Cao Cao to crush Liu Bei rather then oppose. They stood, Cao Cao took a gamble and it didn't work, he withdraws, it happens. Should also be noted that Jia Xu's alternative plan was not without it's flaws so there is no 100% route for Cao Cao.
“You, are a rebellious son who abandoned his father. You are a cruel brigand who murdered his lord. How can Heaven and Earth put up with you for long? And unless you die soon, how can you face the sight of men?”