Inter Milan is the better side based on the current performance. Atletico Madrid just lost a game against Cadiz which means they are coming into today's game with a low morale. But Deigo Simoene is known to be a smart tactician who knows how to exploit counterattacks if there is any opportunity. Inter Milan has been having a splendid season and they are coming into this game with a win over Bologna. Inter made it to the finals last season and they are in good shape to achieve the same feat this season.
You don't compare league matches with the champions league because these are two clubs from different leagues that doesn't Play frequently so you can't judge the both teams base on the outcome of their previous league matches and moreover, Atletico Madrid is known to be very good in defending rather than attacking though Inter Milan seems to be giving Atletico Madrid a tough play in this game and of which they were able to score before Atletico Madrid equalized but believe me, Atletico Madrid doesn't joke with their home ground so it's either they would play to maintain this score or they might even win Inter Milan.
Let's forget the consistency of Inter Milan in their league matches, if you watch the group stage matches you would know that Inter Milan struggled before they were able to make it to the round of sixteen and in recent years, the Spanish teams have been dominating in the champions league so it wouldn't be a thing of surprise to me if Atletico wins Inter Milan in this match as they are already 1:1 in the break so let's see how the second half would turn out to be.