The question is a tough one to answer: it's like asking if you prefer Van Gogh's Starry Starry Night or Sunflowers. Everyone will have their own opinion, and for different reasons.
But we thought we'd get the debate going with a look at the sides in question, using the starting line-ups from the 2009 and 2011 Champions League finals, and the 2015 Champions League semi-final first leg which saw Barcelona crush Bayern Munich 3-0.
The 2009 vintage
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On reflection, the 2009 vintage had a slightly ramshackle defence. Gerard Pique was still relatively inexperienced alongside an auxiliary centre back in the form of Yaya Toure, while Sylvinho was good going forward but a touch suspect at the back. Carles Puyol, the most natural defender of the bunch, was stationed on the right – where he remained highly capable but was a touch susceptible to pace. Having said that, the aggressive pressing system that was deployed by Pep Guardiola put huge emphasis on winning the ball high up the pitch – and thus, any those defensive deficiencies were mostly negated.
The 2009 team’s midfield and attack were superlative in the extreme. Sergio Busquets was a revelation at the base of the midfield, shielding the defence when required and setting their tempo from deep. Ahead of him he had two of the most exceptional midfielders of any generation – Xavi and Andres Iniesta. Their threat was multifaceted – they could retain the ball and pass their opponents into submissive daze or pick apart the tightest defences with accurate through balls; while their commitment to defence was almost revelatory.
The front three complimented each other perfectly. Samuel Eto’o was a ruthless finisher, whose willingness to run in behind opened up space for Thierry Henry and Lionel Messi, who tore in from the wings at will.
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The 2011 vintage
The side from 2011, who claimed a league and Champions League double, had a much more settled-looking back four. Dani Alves is less of a full back and more of a marauding number ten stationed at right-back with strong defensive capabilities and incredible recovery pace. Eric Abidal was reliable on the left but also offered a threat going forward while Javier Mascherano was the perfect foil for Gerard Pique.
The midfield was intact from the 2009 team while Messi had developed into a devastating false nine. He finished the season with an 53 goals and 24 assist in all competitions. His brilliance was acquiesced by the lavishly talented pair of Pedro and David Villa. In terms of personnel, it is tempting to favour the 2011 team over the 2009 side but the very fact that the 2009 team managed to win the club’s first treble gives them the edge.
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The 2015 vintage
At the back, Alba is an upgrade on both Abdial and Sylvinho; while Mascherano and Pique have developed their understanding further and Alves remains as effervescent as ever. While the loss of the controlling influence of Xavi could have been debilitating, Ivan Rakitic has actually come into the side to add another dimension. Barcelona still monopolise the ball better than any other team in world football but the former Sevilla man has given Barcelona a touch more dynamism – which their much-vaunted front three have fed off.
Up top, the potential of Neymar, Luis Suarez and Messi knows no bounds. Luis Suarez has an insatiable work ethic coupled with incredible skills - it is almost as if he has the mindset of a journeyman forward busting a gut to get further in the game, Neymar is defined by an unpredictability that is bordering on impossible to defend against, and, well, Messi has become, unbelievably so, a better footballer this year.
On paper, the 2015 version is the best Barcelona side – all they have to do now to confirm that fact is collect a fourth Champions League trophy in nine years.
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