Follow up with details to that:
As of right nowt the gist of the matter is
By default, Firefox now creates up to 4 separate processes for web page content. So, your first 4 tabs each use those 4 processes, and additional tabs run using threads within those processes. Multiple tabs within a process share the browser engine that already exists in memory, instead of each creating their own.
You can definitely see how the memory fills up when you open new tabs, but it's just around 200 MB per tab and I have 16GB, so I am not worried about it. In fact, I raised the 4 processes limit to 8 processes and so far I haven't noticed any issues. The only thing that I feel like you trade for the crash resilience, is performance for forking new processes whenever you open a new tab (while you're under the limit of course). I can clearly see the allocation happening in the browser's tab bar, but this might even be due to my suite of addons that I have installed. 
I'm using Nightly. It's stupid fast!
Chrome operates out of ram and firefox runs out of the activity space on your spinning rust.
Firefox runs on old tech, Gecko rendering engine. Safari and Chrome use the WebKit rendering engine.
why can't firefox do the same?
Because they're on different codebases. Firefox is implementing new engine features in the release candidate versions that really speed things up.
This question is basically "why isn't firefox chrome"
yeah man!
But Chrome is probably also not getting less chromier.
True the code is open source....But actually making matching code takes brains. Without brains you're a spoon feed cripple.
spoon feed cripple , new movie coming out this fall
of course chrome continuously improves, it has google's money to back it up, nothing wrong with that.
The focus of this thread is to understand how come firefox isn't as good, and in my opinion it is because there's not as much money being poured into it, imo it is improving, sadly at a slower pace.
This is actually more important than it seems. If one company can directly or indirectly control the development of a software that has a monopoly in its field, they can basically decide what becomes a standard and how.
This is kinda sad: http://www.omgubuntu.co.uk/2017/07/firefox-marketshare-falling-off-cliff-former-mozilla-cto-thinks-knows
We just need to spread some propaganda about how Firefox is much better, faster, secure, etc. I believe there are enough people who would buy that, even if it's not true.
And now for some good news: http://hexus.net/tech/news/software/108229-firefox-quantum-flow-big-impact-app-loading-memory/
If you're on the Nightly build you can probably see some of the improvements. The thing is just blazing fast.
That drop is an insane improvement 
It is pretty nice 
Check if all the speedy features are enabled. Especially on Linux. Like Hardware Acceleration and Multiprocess Windows.
