I pre-ordered the white one because I'm looking for something different from the traditional Verizon Black Droid phones which I've had for the past several years. And also because you know what you're getting with the white version. I still don't know what the US blue version will look like. Metallic? Purple? Peeling issues? etc. I just don't know what it will look like. If you get the white and then see that the blue is super-cool, then you can try to switch over within the return period.
One other thing is that I assume the white will garner a bit more attention as well (which may or may not be a good thing).
Either way, it looks like a sweet phone. Good luck with your decision!