I'd use both. Have the content on the emd and get that domain indexed, canocalise it to be sure, redirect the brand domain to the emd but brand the emd content with the brand name rather than the emd name. So effectively, the emd only ever appears in the address bar, not on the site.
The emd will handle search traffic, but you can use the brand domain for the contact info and any offline marketing stuff, articles, sigs etc and hopefully any links incoming will also start to mention the brand. Then if over time, your brand really takes off and becomes an "authority", switch the content to the brand domain and 301 the emd :)