I think both fare well enough and not too far from each other. For the looks, I personally prefer the Nzxt, and I've heard cable/drive management in it is also quite well done. On the other hand, the 450d gives me a better feeling regarding constructive quality, and unless I'm mistaken it's also a bit bigger.
If I had to choose, however, I'd go for the 450d, although I'm biased by owning a 350d and finding myself awesomely with it...