I absolutely love the first half of Batman Begins, but I'm not a huge fan of the second half. We get a great introduction to the new serious, "grounded" Nolan Batman, but then it starts to morph into more of a comic book thing by the finale. To me it seemed like they were hesitant to go all in and remove the "fun" from Batman. As if someone got cold feet and worried that audiences wouldn't like it.
The Dark Knight on the other hand clearly doubled down on the gritty realism vision. They stopped trying to make Gotham look like the comics and the tone stayed pretty serious. I think the start of Begins had higher highs, but as a complete package TDK is better.
Obviously Batman as a concept is totally unrealistic, so when I say "realistic" I'm talking in relative terms.