This will be a tough question to answer, as we are comparing two sides of the club from different eras.
Pep Guardiola’s Barcelona is potentially the greatest side the world has ever witnessed. However, these days Guardiola’s status as a world-class coach is argued now and then. He is criticised for not giving himself a challenge rather than managing a well-established side. But, when he took over Barcelona, they had gone trophy-less for two seasons, which was a concerning situation for the club as they were crowned as Champions of Europe in 2006.
Lionel Messi was just starting to get some recognition as the Argentine was yet to perform with his full potential. Pep witnessed something in the young Argentine as he offered him more space to play when he sold Ronaldinho and Deco. This seemed to be a very bold move from the young manager, but he had such faith in him, that it proved to be a masterstroke. Messi now was accompanied by two other experienced masters of the game, Thierry Henryand Samuel Eto’o. These two perfectly suited Guardiola’s plans as they combined well with the little genius to devastating effect.
Victor Valdes was cool as a cucumber when positioned between the sticks. But this vintage side had a slightly decrepit defence. Yaya Toure, an auxiliary centre-back was accompanied by young and fairly inexperienced Gerard Pique, while Sylvinho possessed a great threat in attack but lacked the defensive work. Carles Puyol, the leader of the team contained the defensive prowess of a natural centre-back. He was deployed on the right side of the backline, where he bossed the defence but sometimes failed to match the pace of his opponents.
In the midfield, Guardiola planted his two generals in the form of Xavi and Iniesta, who perfectly matched his philosophy as they were fresh academy graduates from La Masia. This duo had unique chemistry which laid the base for the foundation of Barca’s dominance. This duo dominated the midfield and if they got themselves in trouble, a young and reliable Sergio Busquets was stationed between the defence and midfield to control the tempo of the game and to shield the defence when required.
By 2015, Barcelona hadn’t won a Champions League title since lifting the trophy in 2011 under Pep Guardiola. In the summer of 2014, Luis Enrique was appointed as a Barcelona coach. The board backed the manager as he was part of the club for 8 years during his stint as a player.
This Barcelona side was different from the 2009 and 2011 squads in many ways. Ter Stegen was signed from Borussia Monchengladbach to compete with his teammate Claudio Bravo in goal as they were regularly rotated throughout the season. Ter Stegen’s start to the season was far from perfect as he lacked confidence while playing out from the back. But he proved his worth by making outstanding saves which were very crucial at those moments.
Jordi Alba was an upgrade over Abidal and Sylvinho, the heart of Barcelona’s defence was safe in the hands of Javier Mascherano and Gerard Pique. The former Liverpool man assisted Pique in their second Champions League final and was exceptional throughout the game and showed quality whenever needed with some great tackles and both of them developed a strong understanding between them. Meanwhile, Dani Alves was as effervescent as ever, creating havoc in the opposition box along with Jordi Alba by targeting crosses for the MSN.
The Messi–Suarez–Neymar connection was an irresistible strike force in Europe. The trio developed great chemistry on and off the pitch as they contributed over 120 goals among themselves. Opponents always felt a threat whenever these three were running towards them which we witnessed when Pep’s Bayern was exploited when these three combined to score two crucial away goals to reach the final.
The midfield of Xavi, Iniesta and Busquets were part of each UCL campaign but it could be argued that they were at their peak in Rome. Xavi’s inclusion in the 2015 campaign is arguable as Ivan Rakitic replaced him in the starting XI for the majority of the season. Rakitic provided huge support to the front three and played well as a box-to-box midfielder. This team was so dominant that they defeated the champions of England, France, Germany and Italy to win the Champions League in Berlin.
Both teams had similar circumstances such as not being able to win the Champions League, dependant on their star player, decline in dominance in domestic trophies. Both sides shared common names in the form of Iniesta, Messi, Busquets, Pique, Dani Alves, Xavi – whose influence in the 2015 team could be argued.
On paper, the 2015 Barcelona side is better but if you see the circumstances under which Barcelona won the sextuple in 2009, it shows that Pep was building a revolutionary team that would probably become the greatest team of all time.