The capital rivals meet in the first leg of the contest on Tuesday evening, before Los Blancos travel to Atletico for the second leg on Friday evening.
"They are slight favourites for all that can be spent, so they are [favourites]. They're one of the most financially-powerful clubs out there," Suarez told AS.
"It will be a tough game. We're two teams who respect each other a lot. We arrive to the game well. Winning the Carranza gives us security. We really want to win.
"It's going to be very difficult. We know them very well. They have signed great players and it will be a nice, hard, tough game. The team who make the fewer mistakes and concentrates more during the 180 minutes is the one more likely to take the trophy."
Atletico won their first La Liga title since 1996 last season.