Barcelona is a big favorite actually, their odds is @1.65, draw @4.33 and Atletico Madrid @4.50. Both of them are strong, Atletico Madrid past history is as good as Barcelona, but they're just underrated. Bet on draw or Atletico Madrid seems worth for the risk.
Simeone only good in making the opponents get angry because Atletico Madrid's players are really harsh and he like to use parking the bus strategy instead of attacking, hence draw is possible to happen.
The odds given by bookies for both teams seem to say that Barcelona will win easily, is this a trap? because after all Atletico is a big club and considering this match is a semifinal I don't expect bookies to give odds that high.
We also have to consider Barcelona's defeat in the first meeting of La Liga, it is possible that such a result could happen again.
I know Barcelona will dominate the game but Simeone is a genius coach in relying on counterattacks. I will consider your betting options a draw or Atletico wins.