It's a very good choice, I'm leaning heavily towards Dembele because he's a player who's already won the UCL and also had the opportunity to reach the final of the Club World Cup, he's a league champion and has won much more than at least Yamal, who is still a child because he still needs to mature a lot, giving him an award now with almost nothing he's won would be doing him a disservice.
Dembele not only won Champion League but success leading the top scorer for PSG and I think right choose if win Ballon D'Or, not matter with PSG failed at FIFA Club World Cup but reached the final stage still the best achievement for giving him Ballon D'O winner.
Lamine Yamal not won Champion League and Barcelona's top scorer leading by Raphinha and I think better him if be the winner than Yamal, however depend on vote which the right player win Ballon D'or wish this time not any controversial by voting for players lack contribution for team and leave the player won many tittle exactly Champion League.