Speaking on a Periscope live Ighalo - who has scored four times since joining United on loan - said that although he had huge respect for the two goalscorers, Van Nistelrooy was his favourite.
"I would gladly pick Van Nistelrooy," Ighalo said. "Van Nistelrooy is a goalscorer. He does not show skills, he does not try to dribble and all that.
"He's a position striker, like me. A striker who can run between defenders and have space. That's the kind of striker I learn from.
"Don't get me wrong, Van Persie is a good player. He scored with both feet, he does everything. But Van Nistelrooy is a striker who – when he's fit – can guarantee you goals in every game.
"He runs between defenders, he can score goals, he takes his chances. So I would choose Van Nistelrooy as a proper No.9 centre-forward."