Here is a look at both of their seasons so far:
13 points clear of Real Madrid, the La Liga title race is turning into a damp squib such is Barcelona's control of the division. The Catalans needed a good season after missing out on both the Spanish title and the Champions League last season, and Tito Vilanova's first one as coach is going according to plan, prior to the breaking news he has had to step down due to illness.
Barcelona's proud record in La Liga stands at played 16, won 15, drawn one, lost none, with a goal difference of +36, 11 higher than the closest the league has to offer. Atletico Madrid are in second, but they remain nine points behind. Already this season Lionel Messi has scored a phenomenal 25 league goals already this season, 13 more than the highest of any player in the Premier League, while he has another five in the Champions League.
Vilanova has made changes in the team at full-back, with Adriano replacing Dani Alves, with Jordi Alba fitting in seamlessly at left-back. Arsenal have been knocked out of the Champions League by Barcelona twice in recent years, to compound their 2006 final misery. This season they look better than ever, and while a defeat to Celtic showed they are fallible, most Arsenal fans would not be overly optimistic should they meet again.
Fresh from losing last year's Bundesliga title to Dortmund and being thrashed 5-2 in the Pokal Final, Bayern faced a huge challenge to regain supremacy in Germany. So far it is all going to plan, Bayern are 12 points clear of Dortmund at the top of the Bundesliga, and nine points ahead of second place Leverkusen.
They have lost just one game in the league, scored 44 goals, and conceded just seven. In the Bundesliga new signing Mario Mandzukic is joint top scorer with nine, alongside Thomas Muller - who has also provided seven assists, joint highest with Frank Ribery. Toni Kroos has emerged as a key man in attack, scoring six league goals, and Bastian Schweinsteiger is in superb form scoring four from midfield. There has been a transformation from last season, 2011/12's key man Mario Gomez has scored just twice, having fallen out of favour after getting injured, while Arjen Robben has played just five league games, failing to register a goal or assist.
Put simply they are running riot, and are the most dangerous team the Gunners could look to face this season. They are a wounded animal after last year's penalty shootout defeat to Chelsea, and are determined to make up for their defeat on home soil. Last time they suffered such heartbreak was 1999, and they bounced back two years later to win the trophy. Arsenal will be well advised to stay out of their way.
When you look at Arsenal's other options, there really is no easy draw available, which will frustrate fans that the club did not go for the win against Olympiakos in the last round to clinch top place in their group. PSG are more dangerous than ever before, led by Zlatan, Lavezzi and Pastore, and will have Lucas Moura arriving in January. Borussia Dortmund showed against Manchester City they are a side to be feared, with Robert Lewandowski the man to fear. Juventus showed against Chelsea they are formidable opponents, especially in Turin, leaving perhaps Malaga as the best option. But Santi Cazorla's former side won't be easy opponents, as they showed recently with a dominant 4-0 win over Valencia - Who are in the competition's second pot along with Arsenal.
Who would you like Arsenal to draw? Could they beat either Bayern or Barcelona?
image: © El Ronzo