The ex-England U21 international has no plans of returning to the Premier League anytime soon.
"I thought the football would suit me better and it has - I have improved enormously," he said.
"The quality shown by Bayern and Dortmund in the Champions League shows how good the league is. I definitely think the Bundesliga is at least on a par with the Premier League.
"I felt as a player it would improve me and that it would be the perfect challenge because football is a short career.
"All the better teams in England try to play football, but every team in Germany plays football no matter what level they are.
"You have to play from the back and I think that's been the biggest difference between the leagues."