If I was an Uchiha member, I wouldn't spend half the fight talking about how powerful Perfect SUsano'o is while wasting so much chakra trying to get it onto the battlefield. I'd rather just quickly give a Sexy Sharingan gaze onto my target and take it to Obito's Pocket dimension. Easy as that.
/Kamui's more useful. Especially since we learned that Kakashi can send large objects to the Pocket Dimension. So instead of fighting a big ass opponent, I can just send it away to a dimension where they could die of hunger.