Why do you say that Firefox 4 is not as vertical-space efficient as Chrome?
Right click on your tabs, and select 'Tabs on top'. Right click on the Menu bar and uncheck 'Menu bar'. Done--looks like Chrome!
Right click on your tabs, and select 'Tabs on top'. Right click on the Menu bar and uncheck 'Menu bar'. Done--looks like Chrome!
EDIT: oh, found it, but my tabs were already on top.
Problem is, Chrome also does away with the title bar.