I agree, hans and james did great job of composing for both batman begins and the dark knight and i to would not change those composers for david in hindsight although it would have been really interesting to see what david would have done with it. I think david completely complements christopher nolans style of film making and the themes presented in each film and i really look foward to their next collabaration, their partnership reminds me of the great composer/director relationships akin to the likes of steven speilberg/john williams or steven soderberg/cliff martinez etc.
I tend to think David Julyan's scores leave a brooding quality. Something mysterious and something that is inviting to curious listeners. It works very effectively for the films he has scored for Chris. I do think that the mysterious tone, that sense of foreboding, does not lend well to Batman Begins and TDK, which I think were very well done by Herr Zimmer and Mr. Howard.
I would certainly like to see Julyan get the chance to score a Batman film, but I don't know if Julyan's style of film scores would work for a Batman film. Julyan doesn't really create "themes" like Zimmer and Newton Howard do. His scores are more like "tonal washes" which work best for smaller films.