DW MX 2004 has better plugins, better interface (imho), better integration (between fireworks, flash, etc), better code (css/javascript) and formatting of it, and better site reporting (W3C compliance, link checking, etc)
Go live has a better File Browser...thats about it though and the only thing i hate about DW is its file synchronization, it still doesn't always work 100% of the time seems like.
thats my opinions from my experience at least.