Barcelona has difficulties scoring goals, while Real Madrid scored 5 goals against Atletico.
I know that some of the goals scored by Real were a little bit lucky, but that doesn't mean that the attacking players of Real are weak.
Real Madrid is the clear favorite for winning the Supercup of Spain. They will become even stronger, when Mbappe joins the squad in the summer. Barcelona probably needs a new coach and several new players. Xavi can't find a way to make the team score more goals.
On paper, Real Madrid is probably the favorite to win the Super Copa. but Barcelona will work hard to win it. because in La Liga it seems like this season Barcelona is unlucky so they will do their best to improve this season by winning the Super Copa of Spain.
I think that Barcelona will give it all to win this as they have almost zero chances of fighting back to get the title during this season as they are pretty away in the gap to leaders that are Real and Girona.That is why I think Barcelona will fight much harder than Real but Real surely this year is in better conditions and their players look a lot more better Anyway this are just assumptions as when these two teams face each other any result can happen no matter which conditions are the teams.