Quote Originally Posted by Abdula
You're the one who is lacking logic. Oro doesn't get his power from the body he uses, the host body has to be strong enough to be able to withstand his power though which is why he needs a strong host. The very reason he was "sick" before was because the body he was in wasn't strong enough to sustain him.

Oro was giving Sasuke power he wasn't using Sasuke's power. Do you think he would have been able to use his hydra technique, probably the strongest technique we have ever seen him use, if he was out of power.
Quote Originally Posted by Abdula
Oro used his body transfer jutsu as usual and just lost the mental battle to Sasuke. Once Sasuke was out of power he gave control over to Orochimaru who was sealed by Itachi. End of story.
In that particular case Oro's jutsu was not completed and Sasuke kept some chakra on all the time to not let Oro finish it (at least that's what it looked like in the old chapter). That means it's hard to say whose "power" actually Oro had, old body's I suppose, but then again that body was dying.

Either way Itachi pretty much pwned Oro back then and it wouldn't matter if Oro was 10%, 50% or 100%.