There's no need to answer FUD with FUD: Firefox's UI does not become unresponsive with increasing number of tabs. Certainly not with just 50 anyhow; I do that all the time and never notice a slowdown. The tab-closing animation is less smooth than chrome's however. And while it's certainly true chrome uses more memory per tab, I can't imagine running into that problem very easily even on somewhat outdated hardware. A 4GB system should be able to do 50 tabs normally, and how much more do you need?
I have a quad-core, 8GB machine at work and a dual-core 4GB machine at home. Both are running Win7 64-bit. How much more do I need?
I have noticed slowdown in Firefox's UI on both machines. More important than number of tabs, is CPU usage. For example my HTML5 heavy trading platform often causes the single-threaded Firefox UI to freeze and slowdown on both machines, while I have never noticed Chrome freezing when this site is open.
On the other hand, Chrome's UI runs smooth as butter until either open tabs or other programs bring memory usage to over 90% Physical Memory in the task manger. Recent builds hit that wall a lot quicker than it did a year or so ago.
I am a Firefox users so this is not coming from a bashing Firefox POV. I could open 100 - 200 Tabs in Firefox without problem if i disable Javascript and all Add on.
As soon as you have some heavy JS usage website, even 50 Tabs can slow down the UI. This is on Quad Core Ivy and 8GB Ram with SSD.
The amount of JS on one website now is getting insane. Chrome have similar problem as well like the OP have said. Just a different one.
The FUD is that the # of tabs has anything to do with it. Also, these problems have been getting a _lot_ better with recent releases, which are much better at avoiding blocking the UI thread. It's not perfect, but it's not something you see very often either. Let me put it this way: I can't even remember the last time I've had a UI slowdown, and I use FF on various machine with lots of tabs all the time. (Firebug's still really slow, though).
So when you say "some heavy JS usage" what exactly do you mean? Certainly not stuff like google docs/mail/calendar, and they're all heavy on the JS...
