- Edited
Definitely Option 1, probably followed by option 4.
The main factors that influenced my rating:
- They shouldn't look like static buttons — tabs are dynamic and can be added and removed frequently, unlike the other buttons in the toolbar. Options 2 and 5 fail this criteria, IMO.
- Should feel like it belongs in the toolbar — Option 3 doesn't feel right to me (the toolbar is otherwise quite flat on the Z axis; adding a drop shadow is weird to me), and option 5 looks fine except that the "tab" visual metaphor doesn't make as much sense when it's disconnected from the page's contents like this).
- Should feel self-consistent and contiguous — In Option 6, the currently selected tab causes the tab bar to feel like two discontiguous sections to its left and right, rather than a single bar. Rather than "This tab, of n tabs, is selected" it feels like "You are here, but these are some tabs you could click on instead. Also, here are some other tabs." Option 2 also feels like the tabs are quite disparate: they are each self-contained, with gaps in between them, rather than feeling like a single row.