Odds are not too big different and all four clubs are nearly similar in competitiveness. They will not only compete with each other but there are other big clubs and underdogs can challenge them in this season. To go to the final match, PSG, Barcelona, Real Madrid and Liverpool will face with many strong opponents and perhaps one of them will join the final match with another club that is not in this list.
PSG are the champions last year, but I'm not sure they can repeat that this season. I'm more confident in Real Madrid, Liverpool, or Barcelona. Although this is just speculation, I think they have very good statistics for the condition of the players they have at the moment. But beyond the statistics of the players they have, this may change. Because every game always has a different path and player statistics are only predictions based on the quality of players, which always changes in every game. The current competition system also makes it possible for anyone to advance to the knockout stage.