Madara's words to Hashirama:
"I will keep you for a little longer"
He can beat Hashirama anytime he wants, and Preta path can cancel Mokuton. Madara is just enjoying the fight a bit longer before he becomes a Jinchuruki. He hasn't played his trump card yet, and in his own mind we saw him think "I want to beat Hashirama before becoming Jinchuruki"
Sorry guys, but Hashirama is going down. So are the other Edo Hokage's, once Orochimaru comes back...
Hashirama was better than EMS Madara, but the point is now that Madara has Rinnegan, Edo body and Mokuton. Hashirama is visibly struggling in their fight. Madara will probably only win because of a cheap shot from Obito, Sasuke, Orochimaru or someone else.
Best logical argument? Madara has unresolved plot (his trump card, how he survived the VoTE fight, becoming 10 tails Jinchuruki, dialogue with Sasuke, etc.) Madara wants Hashirama alive long enough to see him become the host, that's it. Past that he will wipe out Hashirama and have Orochimaru, his true accomplice, take out the Edo Kage.
Orochimaru was no match for Itachi or Madara, so he agreed to follow Madara for information on the Sharingan, some Hashirama DNA and for the shits and giggles of it all. How else did Oro get the 1st's DNA? Sorry guise, but fanboyism delusions gotta answer to reality at some point... Madara will win.