Funny to see Chrome lose. Nice to see Opera is okay.
Well that understandably because chrome use lot more ram with each new tab like separate process and shit like that.
Exactly, and this is better in real life because if a tab/plugin crashes, your whole browser won't crash.
Yea but even if crashes, FF/Opera just restart and load again everything like nothing happened 
That's the whole point. You don't need to restart your whole browser. Sometimes there would be a video that's taking forever to buffer, so I let it buffer in another tab. If I go to another tab, and then it becomes unresponsive, only that 1 tab will crash, and my video will keep buffering. In your case, you would have to re-buffer the whole video again.
Also, Chrome is better in the fact that if you open say 20 tabs, both browsers ram will go up significantly. Now say you close 19 of the tabs on both browsers. On firefox, the ram will still be quite high (higher than what it should be for 1 tab), but on Chrome, the processes for all the other tabs have ended, and the memory is what it should be for 1 tab.
