They have yet to REALLY fight. Iron Man fought Hulk. That was a fight (Hulk would NOT have lost but, whatever; Robert Downey starpower too strong...)
Thor has not really fought Hulk He tried to reason with him and get him off the Hellicarrier. He was losing though, but if someone is throwing Haymakers at you the whole time and You're just trying to get them to calm down, of course you're going to take some shots.
But fear not people, I truly believe we'll see an all out Hulk vs Thor battle in Ragnarok.....or at least I'm hoping so.
Even if not, Thor has higher highs and lower lows . But if he uses his powers he wins this. Slugfest gets him the loss.