With the matches both teams have played so far, I think Juventus is stronger than Inter Milan when it comes to defense because Juventus did not concede a single goal in their last three games, and they scored six goals, on the other hand, Inter Milan has scored 8 goals in their last three games and conceded two against Genoa, both teams have drawn one of their last three games, but Juventus did not concede any goal, which is why I think they are stronger than Inter Milan at this point.
However, AC Milan began to struggle at the end of last season, I have never seen a team perform as poorly as AC this season, even Napoli, which was bad last season, won their game. The match against Inter Milan will be difficult to predict because it is a derby match, but as Inter Milan is in better form this season and has a good record when playing against Ac Milan, I believe Inter Milan will be the favorite to win because Ac Milan lost to a team that was promoted to the league this season, so they will be unable to withstand the pressure of Inter Milan.
Last season up until a point Juventus looked like a good team as well, but then it ended up not being like that and they started to do a lot worse. The sad thing is that they were leading the league for one or two games as well, and then they ended up going on a 10 game terrible streak and finished third place instead. Juventus starts the season very well, it's the lack of depth that causes them issues, because by the middle of the season they have players who are doing not that great and because of that they end up being not that great neither.
I suggest that they should end up doing much better with depth and this season it looks like they have a chance for that. Lets see if they can actually do fine, if they can do fine then it shouldn't be a big issue at all. Fatigue and injuries and cards end up making a team so much worse, and if they can adjust their team better and can go for the entire season at same level then they could definitely win the league.