Blac 32GB - Having been hitting the 16GB limit for a while, it's nice to have a bit more headroom. I remember having a pretty heated debate whilst inline on the opening morning, about whether to get 8 or 16 (16GB models sold out quick as stores had much more 8GB handsets than 16) - same logic, same reasoning - i'd go with the highest you can get.
The new model does video too, so it would be nice to have some more space to store video on it. With 16GB more to play with, that's a lot more podcasts etc too.