From what I've seen this season Barcelona play better as a team. When some of their starting players are unavailable they still can play with their usual tactical mentality. But when Real Madrid has some missing key players their game plan have to change. So this affects everything about them. Barca don't rely on one or two players. Although Lewa is the most important player, when he's not playing Barca still can find goals. Real is having hard times without Benzema for example.
I think this is the biggest different between these two teams. I believe Barca is favorite right now. Things might change but they are the better side now.
You're right, Xavi has really brought his players together at Barcelona this season. When the strikers get stuck, Pedri or Gavi perform well and make Barcelona win with their goals, as well as Dembele or Raphinha.
Tactically, Barcelona has good performance to record many chances to score. The 42 goals they have scored in 20 matches is proof that they are the most productive team in La Liga at the moment. Besides, Barcelona's defense also helped a lot, they only conceded 7 goals in 20 matches. No other team has this kind of defensive power in La Liga, only Barcelona leads the statistical average.