Thinking about it, experience shouldn't be much of an issue. All the players have played at the big level and have played against top teams in the world. Hell, most of them have played crucial games at the World Cup. In this respect, I don't think experience really matters. It's just another big game against a big opponent.
What really does make the difference is tactics and the smartness of players. Liverpool and Milan are some of the best at it and that's why they win so much in Europe. The tactical side of the game is what could've cost them, but Wenger did well to get the best out of his players. When Arsenal plays up to par, they are extremely hard to beat, but when they have their off day, their flair really suffers and can cause them loses. Sides like Liverpool and Milan that have an off day in Europe often over come this by sitting in well and playing tactical football.