Well, things are pretty simple for Verratti. If he wants to have a great career, like the likes of Iniesta, Modric, Kroos Busquets etc. he should push for a move. If he doesn't want to be remembered as one of the best players of his generation, he can stay at PSG until he retires or until he is older.
Right now, he is not developing. He is not better than he was 2 years ago. He is almost the same, because the club itself is not able to break into the best teams in the world group. So, of course there are frustrations, because every player wants to do great things, and be a winner on a grand scale.
Can he do that at PSG? Not really. Can he get paid and be comfortable in Paris? Sure he can. So, it's a matter of priorities. Barca will continue to be great with Serri instead of Verratti because unlike PSG, we have monstrous players in the squad.
How will Thiago Silva be remembered after all these years at PSG? As an underachiever. What did he actually do in the highest echelon of football? Not much. Very little for a player who was once compared with the likes of Maldini or Nesta, while at Milan.
So, for Verratti, it's very much a choice between being comfortable, and being a winner. There are attractions in both things, so his ambition to be viewed as one of the leading players of his generation must overcome the need for comfort and less pressure, which everybody has to some degree. Some make the next step in their careers, some never make it and settle with less for a comfortable career and an easier time.