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.
Inter Milan and Atletico Madrid are scheduled to face off in the round of 16 of the UCL. Judging both teams, they're good in their leagues. Even though Inter are at the top of their league whilst Atletico aren't, both teams still have the capacity to make the game fierce for themselves. Both managers are good too and have got experiences too and their squad are good in their own separate ways.The game would be fierce, predicting a winner would be difficult and definitely both team odds are high.
For their domestic leagues, Inter are still on top and there's not really much threats because they're able to subdue other teams even though the games are sometimes tough especially for Juventus following them closely, they've got a work to do to stay on top of they really want to lift the trophy. For Atletico, they've got 3 teams ahead, so their struggle will only be to finish in the top 3/4 spot because currently they've not gotten any glimpse at the trophy and I doubt that the teams ahead of them will give them the leisure.