Black version of Souryuu City all the way. I really dig the electronic feel it gives. Black City's got a modernesque theme to it too, and I like it better than the bland White Forest.
I find myself liking more tracks in this game than from any other Pokémon game. The soundtrack is exceptional.
I totally agree. The Black City by itself is something that's never been done in a Pokemon game before (I think, right?)
The track that I've really taken a liking to is the Team Plasma battle one. Something about it just sounds so awesome. As a whole though, this game is probably the first Pokemon one that I've taken notice of the soundtrack and actually enjoyed it. They did a great job on it.