If we're looking at their La Liga form Madrid is the favorite IMO. But it's hard to use that as a basis since we've seen many teams outperform their stats when they're in a final. Since Yamal is back I also think Barca can put up a decent fight. I'm going to pick Madrid as the favorite, but I won't be surprised if Barca wins this. They need something more to get the momentum in their favor again to win more titles this year.
Yamal return is very good for Barcelona but there is still time and matches before the final match between Barcelona and Real Madrid. By his sensitiveness with injuries recent months, he has risk to get another injury and miss that final match. Barcelona need to protect Yamal if they don't want to lose this player for that important match, one match decide a title and they truly need Yamal for it.
Real Madrid have better form recently and they don't too much rely on one or two players like Barcelona. With Real Madrid, they can have different quality replacement for Vinicius or Mbappe, but with Barcelona, if Yamal is out, they have big trouble.