Comparing these two palters is not right but I think Dembele can have much better performance in PSG than Neymar during the time when he was playing for this team, especially because we know Dembele left Barcelona because Xavi didn't believe his skills at all and this player is even more motivated to have better performance to prove himself. Also considering the age of Neymar and Dembele, we know Dembele can be a good investment for PSG in the next years.
PSG have good players that would surpassed the actions and performance of the former ones. Ousmane Dembele and Neymar Jr are almost the same pairing interms of physiques and crucial abilities on the pitch. PSG have troubles with Neymar Jr because he was inconsistent in league games, always vulnerable to injuries that would ruled him out for months and missing half of the league. The parisians boss, Luis Enrique will make things work a little bit faster for the Frenchman, he knows basically how to utilized Dembele's performance to blend with his ultimate objectives.