The Dutch winger had the choice of both clubs as he left Celta Vigo and opted for the Premiership club: "Manager Steve Bruce was much more convincing than Henk ten Cate and Martin van Geel.
"According to the manager, I looked like Ryan Giggs and I could be just as big. He was great."
Asked about his relationship with new Brum boss Alex McLeish, De Ridder told De Volkskrant: "He said that I'd be better in a team that plays football with better players around me.
"You could almost believe that I would be better at Manchester United."