Back during the September CTP, I would have recommended Expression Graphic Designer over Illustrator. It was a great vector editor, plus it had some powerful pixel-editing features that couldn't be found anywhere else.
However, the powerful pixel-editing features have been removed. Expression Design is a crippled remnant of what it once was-- it's now geared only towards generating graphics for WPF projects. The current version is definitely one to skip.
I liked Expression Web as HTML editors go, but I haven't used Dreamweaver (so I can't make a comparison), and still prefer using a text editor for HTML.