Lets see... - For Obito's plan Naruto was more useful then Sasuke, And for his plan to be success Naruto needed alive, hell Sasuke was basically irrelevant. - Obito had no way to know that Naruto will able to master either KCM or BM putting him on same tier as EMS Sasuke. - Even then Obito gave Sasuke EMS, who btw wanted to kill Naruto, whom Obito has no knowledge can defend himself against EMS Sasuke if they fought. So what if EMS Sasuke had fought a Naruto who had no KCM or BM and killed him? Obito's plan would've been fucked. And i'm not even bringing Obito saving Sasuke during FKS which led to formation of allied shinobi force which lead to his defeat.