Now with DC United, Rooney won the Champions League with United in 2008 and believes City, seeking a quadruple under Pep Guardiola this season, can reach the showpiece - which will be held in Madrid at the Wanda Metropolitano - for the first time in the club's history.
"I'm gonna go with Manchester City v Barcelona," Rooney said. "I can tell you who I want to come out on top, obviously I want Barcelona to win if it was them."
Rooney suffered defeat to Barcelona in two further Champions League finals, scoring a stunning equaliser in the latter game, a 3-1 loss at Wembley in 2011.
Asked about his experience in the 2009 disappointment, Rooney said: "I think that's what you learn most from, times you've lost in big games.
"I've won Premier League titles, the Champions League but the ones I look back on are the ones you've lost.
"You always look back and think you could have done something different, they're the ones that stick with you."