At the moment, Inter are still quite favored because they will fight Real Sociedad which in fact is a club with the status of a dark horse at the moment but that also does not mean Inter will win easily because in the end this is just talking about probability and at the moment their probability is quite large when compared to Sociedad, but it does not rule out the possibility of unexpected surprises like the previous few seasons in the Champions League sometimes there are some unexpected surprises including last season where Inter became semi-finalists because it was a surprise that could not be expected before.
A slight correction in that Inter will be playing against Atletico not Real Sociedad as they were already in the same group before which meant Inter finished second and Sociedad will face PSG in the last 16.
Inter and Atletico at the moment they can still be said to be a big match because after all, currently Inter's performance is in good shape and Atletico also they are actually quite good when compared to the previous season, this season they are better because they are helped by the presence of Morata and Depay for their attack line.
This will be a big match in the round of 16 because after all in terms of experience they can still be said to be balanced, in terms of the quality of their players is also not much different so this is still a fifty-fifty.
As for Sociedad at the moment they are indeed a dark horse club which is indeed very good even they can get the top position defeating Inter, Benfica and Salzburg who are subscriptions and I think being in the round of 16 with group winner status for a debutant club is quite impressive for Sociedad.