Which one is/was the strongest league?

The Premier League? La Liga? Serie A? The Bundesliga?

The only published scientific information available is from 2005 by Bloomfield et al. (1) (-see reference below) and considered different aspects of the respective players in those four leagues.

Firstly, 2085 players from the leagues were identified that have at least one international cap and therefore included in the study. Data from those players (age, height, weight, BMI, playing position, international goals scored and FIFA ranking) were collected. With regards to those specific items, the Premier league inherent the highest number of international players, followed by La Liga, Serie A and the Bundesliga. However, the Bundesliga presented the tallest and heaviest players. Average height was 1.83 (±0.06 m) and weight was 77.5 (±6.4 kg). The shortest players were seen in La Liga and the lightest in the Serie A.

Interestingly, the most foreign players in general were seen in the Bundesliga (49.8%) followed by the Premier League (38.1), La Liga (33.5%) and Serie A (33.3%). In greater detail and probably due to geographical distances, most of the foreign players in Germany came from Eastern Europe (followed from players from Africa), while the greatest amount of foreign players in the Premier League were from Western Europe followed from Northern Europe. The greatest percentage of foreign players in La Liga and Serie A came from South America.

It seems that the Premier League hosted the most experience international players with each players had on average 25.5 international appearances, followed from the Serie A (24.4), La Liga (20.4) and the Bundesliga (19.7). However, most goals scored by those internationals were seen in the Serie A, followed by La Liga, the Premier League and the Bundesliga. Similar ranking were seen for the FIFA world ranking of the players, leading with the players from La Liga, Serie A, Premier League and the Bundesliga again the last two positions.

As a result, the authors came to the conclusion, that La Liga contained the highest quality players, however, the Premier League the highest amount of international players and the Bundesliga seemed to be the league consisting of players with greatest physical appearance.

It seems also plausible that players with a certain heritage choose a specific league that might possibly benefit their playing style. As it was mentioned earlier, players from South America were predominantly present in La Liga and the Serie A, while players from Eastern Europe were more seen in the Bundesliga.

We would like to reiterate that the data (partly from 2002) was published in 2005 and further elaboration on that topic might be desired. It would also be interesting to see differences in budgets (and therefore healthiness of the clubs), maybe even spectator appearances and other information on time-motion-analysis (including information such as passes completed, distance covered etc) to show differences of the mentioned leagues.