Mikhail Arkhipov is a dev manager on the Visual Web Developer team, who posted recently about some of the differences between the VWD features in Visual Studio Code Name Orcas and the features that are in Expression Web. He has a good list, with some interesting insight into how choices were made about what features should go into what products.

One key point he omitted in his list was that we are really creating two different products for two different audiences who happen to perform similar and sometimes overlapping tasks. As such, there will often be occasional differences in feature set, but more importantly you'll also see some differences in how we present the same features for different audiences.