As well as home advantage United have another key factor in their favour with City's main man Sergio Aguero set to miss the game through suspension.
Souness told talkSPORT: "I think Man United at home will edge it.
"City, I'm not sure if all the players are grasping want the manager wants right now - that might take a bit of time.
"I'm just thinking the firepower Man United have might be the difference.
"And [Sergio] Aguero not being there – he is a worldy for City and when he doesn't play the stats are very different."