I think that Messi should think of Manchester City as a second option after being free agent in the summer. He would surely prioritize returning to home, Barcelona. However there can still be some hindrances for Messi to go back there. FFP rules in the La Liga can block the way for Barcelona to make this transfer happen. Otherwise Barcelona also wants to sign him again and Xavi also agrees with the board.

If the deal between these two sides doesn't happen then I think Messi should think of Manchester City before PSG - I guess that he wouldn't like to leave Europe soon. Maybe he will need to adapt to a new team again but there is a big difference at this point. The difference is that he can adapt much faster to Manchester City's game plan compared to his first times at PSG.

Because he is already very familiar with Guardiola's system and he can feel like he is playing for Barcelona nearly.