Leaning towards Real Madrid.
As great as Alex Ferguson is, Mourinho is a tactical genius. They have been matched up 13 times throughout their careers spanning from Mourinho's time with Porto til Inter.
Mourinho has won 6 games.
There have been 5 draws.
Ferguson has won 2 games.
Mourinho has Fergies number, he beat him on his way to his first Champions League title and has won 2 EPL titles in the 3 seasons he coached at Chelsea.
Real Madrid, end of discussion.