Atalanta tends to be the favourite in the match considering they have been doing very well in several matches, indeed we cannot deny that since defeating madrid, milan has risen up and are unbeaten in their last 5 matches in all competitions, but as you said they still have weaknesses when facing big teams, so that can indeed be one of the factors for us to favour atalanta in the match later, if we look at the head to head of the two teams so far it looks like BTTS is a good choice, but if you look at their current sharp attack line, over goal can also be a better choice in my opinion.