Settings > Appearance > "Use system title bar and borders".
edit: clarified I meant Chrome.
A full height title bar with the title of the current tab in it that I can use to drag the window around. Having to precisely aim my mouse pointer in order to drag my window is extremely annoying.
Anyway, I fail to see a significant difference between Finder and Chrome's appearance: http://i.imgur.com/sgfMXOy.png
If Chrome was full of tabs, the ~20px area to drag the window around is arguably a bit small, but it'd look ridiculous if there was a huge margin above the tabs.
But why do you think the Firefox tab placement is better?
Chrome and Opera squeeze the tabs, but list them all, whereas Firefox forces a scroll after so many, which feels horrible. Also Opera has let's you list and switch open tabs with CTRL+TAB, or lets you reposition your tabs.
Really though managing tabs should be left to the window manager. Otherwise you just get inconsistant behaviour between applications.
That's when the title comes into it's own.
I use this tiny add-on, written by one of the main Firefox front end developers: https://addons.mozilla.org/en-us/firefox/addon/custom-tab-wi...
It makes Firefox have the Chrome behavior of making tabs shrink infinitely. All it does it tweak one minor setting in the UI, so it's pretty bulletproof.