United have drawn Reading in the third round.
Mourinho said: "I think the Championship teams are much better than before, he told MUTV ahead of the FA Cup third-round tie against Reading next month.
"They are very, very, very similar teams, not just in the potential but the way they play, to many Premier League teams. So, to play against Reading, is no different, to me, to playing against the majority of Premier League teams.
"So it's good to play at home, obviously, yes. One less game to travel to with so many matches. It's better to play in your stadium with two-thirds of our fans so that's a positive draw. But it's not an easy opponent."