Well he did aim to kill Itachi although he was an Edo Zombie. Didn't he almost kill Sasuke with Muki Tensei? Anyways, he had the advantage thanks not only to his experimentation, but his location where the fight took place it amplified the powers he stole to intercept both Sasuke and Itachi. Besides the match was more Itachi vs Kabuto than Itachi and Sasuke vs Kabuto, because Sasuke barely contribute to the fight. He was just there to assist Itachi to help him have enough time for Izanami and save him a few times. You do realize Sasuke didn't use the Full Susanoo, Blaze Release: Magatama, Coated Arrows, he also had to prevent Kabuto from tagging Itachi, and he held more so than Itachi. Kabuto didn't look to me like he was holding back in this match. He was using all the Sound 5's powers, Orochimaru, Taka, and DSM. The only thing is that his jutsu's were less 1 KO's and he was careful in how to use them. Itachi and Sasuke had more complications because one it was the first time they fought as a team and second they had to capture Kabuto with genjutsu. In a way, Itachi was the one that complicated the match by telling Kabuto his intentions. I already said, Kabuto with Edo Tensei can beat the Uchiha's together or solo both of them. But alone without Edo's, Kabuto ultimately loses the match.