SS arc Byakuya > SS arc Ichigo(Bankai)no hollowfication.

Soul Society's Byakuya is Stronger than Soul Society's Ichigo.

The thing is the only time Ichigo really overpowered Byakuya in the fight was when white possessed him. Aside from that the fight was pretty balanced until Byakuya used his Senkei: Senbonzakura Kageyoshi, he literally overpowered him after that. Before anyone says Ichigo Perception Blitzed Byakuya, yes he did but when he was completely off guarded and underestimating Ichigo. Because after that it was clearly shown even in the scene that now Byakuya was focusing in Ichigo's movements by zooming in his eyes and making Ichigo's movements somewhat slow and then he was keeping up with him.

Even in the last clash when both Ichigo and Byakuya were completely exhausted Byakuya used his Shukei Hakuteiken and Ichigo gathered his spiritual pressure around his blade. But at the end Ichigo was the one who fell and Byakuya was able to hold his own and even used shunpo at the end. it was just that Byakuya declared Ichigo the winner our of honour.