Milan just has the heritage in champions league and thats one of they reasons they advanced. Inter has better team but I'm afraid cause Milan is known for it's Champions League performances.
If you look at the experience in the Champions League competition between AC Milan and Inter Milan, of course AC Milan has a better advantage in this regard so there is a high probability for AC Milan to win in the semifinals of the Champions League this season. But I also wouldn't be so surprised if, for example, Inter Milan were able to beat AC Milan in this season's Champions League competition in the semifinals because the two of them will definitely give their all to reach the final in this season's Champions League.