Manly will win this by a couple tries IMO.
Souths are getting killed everywhere except the scoreboard, and only really being kept in it by cheap penalties getting them out of their own end for the last 20 minutes of that half after Manly wouldn't let them make more than 20m per set for the opening 20.
Penalties are currently 6-2. The refs won't even it up, but they also won't want it to blow out to 10-4 or 12-5. Penalties will be even in the 2nd half, and with that artificial territory advantage removed Manly's dominance is going to come through