A team that I consider a favourite today may perform poorly after a while or my favourite player may change. Also, since I have personal freedom, I can keep any club I want on my favourite list. If a team is good I will definitely support it. I'm also not in favour of supporting a team emotionally while people enjoy the game and are there for entertainment. I think my own preferences may change over time. No team should be emotionally supported for entertainment or betting purposes.
This is also what I do, I analyze and determine who will win because I will also include it in my betting list. If later it causes me to lose, that is the risk of a bet that must be prepared to lose. IN the Champions League I am always neutral and judge based on their overall performance, apart from that I will look at the mentality of a club. Because I see in the Champions League the mentality of being one who takes part in the results that the club will get in the future. Because usually a club with a high mentality will be more comfortable in playing, and in a game comfort is something that can bring victory.
Manchester City, Real Madrid are the 2 favorites, Inter Milan is also in my category, apart from that a club like Bayern Munich is also actually one of them, but I personally put a smaller chance.
I do think that Porto would be tough on Arsenal but they'll qualify ahead of them to the next round. I remember the last club that knocked them out of the Europa League Competition last season was Sporting Lisbon. As for Barcelona, they're one team with lot of inconsistency. Could they defeat Napoli? They could finally do that but they will not escape if they fail to sign up a good defensive midfielder. According to Cristiano Ronaldo, Manchester City are his number 1 option to win the Champions League Competition.