In Begins, Gotham has a futuristic/fictional and run down look: think of Oldtown, the trains built by the Wayne Corporation etc.

In TDKR, Gotham looks like plain old real world NYC - we don't see the trains anymore. Oldtown is just a standard poor neighborhood. Lots of the locations used in the movie are easily identified as real world NYC locations: the stock exchange or East River bridges for example.

My question is: Why did Nolan change Gotham city from a shady fictional more cartoon-like town to plain old NYC?