Tabs are imperative to web productivity.

On Google Chrome since tabs are on their own row at the top of the window and maintain their size and position you can fling your mouse to the top of the screen easily hit them. On Safari since the address bar expands from the active tab, the size and position of the tabs are drastically changing. This makes selecting a tab more difficult. Additionally, since the size the address bar is wider the distance your mouse has to travel to select the neighbouring tab increases.

In the end this leads to more effort and bad ergonomics. I would love it if they just had the tabs on one row and address bar one row, until then I will stick with chrome on the desktop.