Real are the more stable team now, they play well and don't slow down, while Barcelona have been rebuilding lately (can't say whether it's good or bad - the main thing is the result). Barcelona's squad is good, no doubt, but will they be able to play cohesively to produce a good result? That will become clear after the start of the season.
In any case, the game will show everything, but the main problem of Real Madrid as a club is that another year, one season has passed. The club's coolest players did not get one year younger when the team was providing results, when Barcelona grew a lot as a team last season thanks to Xavi's return to his hometown club, to his native penates. This season, let's hope that there will be fierce competition between these teams thanks to the simply jewelry work of the Barcelona management this offseason, despite the obvious financial problems. It is also thought that Diego Simeone and his Atletico will bring competition back to the permanent leaders of the championship, which he did not fully succeed in last season.