He said also after that it is not matter anyway =D but OK....
He said it cuz you can manipulate Sasuke much easier, then Obito. (Mangafact)
He also sees current Sasuke in action . That means that Madara compares MS Obito with current Sasuke .That is even a compliment to Obito. +++ Sasuke has no Kamui ( what has made everything easier for Obito )
Obito role could nobody replace
He said it because he is pissed off, because Obito has changed the team. And with Sasuke would it not happen.
He wants Obito back

AHAHAHAHAHA that is even a affront to Sasuke.