Barcelona has clearly been one of the most dominant sides in European football in the past few years. They often play a 4-2-3-1 (or sometimes 4-3-2-1) formation. Is the primary advantage of this formation just that most other sides are still playing with 4-4-2 and so a 4-3-2-1 allows for more presence and control of the midfield?
Well for one, you have the advantage of not being over run in midfield. For example, if you play 4-2-3-1 against a classic 4-4-2 then you have 3 central midfielders (2 defensive, middle of the attacking three) against the 2 central midfielders of the 4-4-2.
Additionally, in a 4-2-3-1 the 2 defensive midfielders can concentrate on providing the defensive shield in front of the back 4, while converting defense into attack, yet not usually getting caught in highly advanced positions, thus leaving the team exposed on the counter. Think of players like Xabi Alonso and Sergio Busquets, who make a living out of playing these positions.
Actually Barcelona uses that formation only on paper. They rarely have 4 players playing as defenders, they kinda use 3 (two central defenders and one full back pass the ball between them and the keeper). Playing like this allows them to have a greater number of players in front (where two of the attacking players sit very wide on the pitch) which is extremely useful if the other team is pressing.
About 4-2-3-1. I guess it's a very good formation because it allows you to use a large type of players on every compartment depending on your needs. In fact this formation is played by teams with a bigger squad (which has very good defenders, 2 or 3 defending midfielders and very skillful attacking players - see Barcelona, Real Madrid, Manchester City, Borussia Dortmund and Bayern's tactics and depth of squad).
It is also a good formation because it allows a larger number of players run freely.
All this information are from talk shows and math analyses.