If Osimhen were so in demand, then some team would have bought him long ago, but he continues to play in Napoli, and all his possible transfers end only in rumors. Sooner or later PSG will win the Champions League, and Ligue 1 remains one of the top leagues that provides many opportunities for the player. Mbappe, by the way, came to PSG from Monaco, and now he is a Real Madrid player, in my opinion this is a very good career development, and it didn’t hurt that he started in Ligue 1.
As far as I know, last season Osimhen had a very large transfer market value which made many clubs unable to get him. Napoli also won't let other clubs get it easily. Because of that, they set a high price clause for Osimhen. This season Napoli's performance has been very bad. Osimhen managed to score 15 goals and was among the top scorers but was unable to provide a good performance for Napoli.
I think if given the choice in my opinion PSG is better than Napoli. They can almost always win the league so they will always be able to play in the UCL almost every season. But the problem is that currently PSG is not a good choice if you want to have a career. They are a good team but Ligue 1 is not as competitive as some of Europe's other top leagues.
If Osimhen's target is a domestic title, then Paris Saint Germain could be an option for him because it is almost certain that they will be able to get the Ligue 1 title. However, I agree that if he cares more about his career, then I think it would be better for him to look for a better team again in competition. It's true, almost every season Paris Saint Germain can be in the Champions League, but every season they also experience repeated failures. they are not that great compared to other teams in the Champions League.
That depends on Napoli too, because if the price they set is high then chances are that only Paris Siant Germain will be willing to spend the money to bring him. The reason is that with the high price, other teams are thinking twice about getting his signature. Last season there were also many teams interested, but they couldn't afford what Napoli wanted in terms of price.