Of course, he has improved in Spain but he didn't need time to be excellent. Indeed, he joined Real Madrid because he was brilliant in Germany in terms of assists/goals and impact on the game.
After Germany, he was successful because he is not a falling star.
To illustrate my point of view:
- 2009/10: more than 55 matches including ... 16 matches with Germany. He played very well during the WC 2010 (he scored against Ghana for instance).
- With Bremen, 108 games in all competitions, scoring 16 goals and giving 55 assists
We are not talking about a child but of a confirmed player in the Bundesliga league. This confirmed and talented Bundesliga player has succeeded in Spain because he left the country at the perfect age (not too young, not too old)
My choice is based on the following post and that is why, I have posted a video about his terrific performances with Bremen.
DFB-Pokal winner in 2009 + DFB-Pokal runner-up in 2010
He lost the final of the Europa League against Shakhtar
The Bremen player who saved Germany against Ghana :