Depends on who you ask. The most important thing to note is that UCL is a cup competition and the domestic leagues are table competitions. Many would argue that the best team is best determined by a table format. IOW, a table requires more consistency and gets rid of luck factors better. More matches = less noise. But, then you have the obvious issue of not facing the best clubs from other nations and also get into the argument of whether the 10th best UCL side is better/worse than the 10th best EPL side and the relative quality of domestic leagues for example.I don't know enough about this to have the answer for myself, which is why I'm asking you more knowledgeable soccer/football fans. Do these teams and players care more about their national league (i.e., Premier League, Serie A, etc.) or the Champions League? Which has more meaning to them and their clubs? Does Chelsea care more about winning the PL or the CL, for example? How about Ronaldo or Messi - which would they prefer to win?
Liverpool: Alisson, Alexander-Arnold, Matip, Gomez, Robertson, Fabinho, Henderson, Keita, Jota, Salah, Origi. Subs: Adrian, Kelleher, Van Dijk, Konate, Thiago, Milner, Mane, Tsimikas, Phillips, Oxlade-Chamberlain, Jones, Minamino.
Milan: Maignan; Calabria, Kjær, Tomori, Hernandez; Kessie, Bennacer; Saelemaekers, Diaz, Leao; Rebic. Subs: Jungdal, Tatarusanu; Ballo-Toure, Florenzi, Gabbia, Kalulu, Romagnoli; Tonali; Giroud, Maldini.