I have the same habit, but the opposite experience: that Firefox gobbles RAM+CPU and Chrome handles them elegantly. (Admittedly, I haven't given FF a new chance in about a year.)
Was there a particular upgrade that addressed process management and/or memory leaks? I also wonder if it's an OS thing (I'm on OS X).
That's curious. I'm quite used to hearing conversations where people have wildly different performance experiences with Chrome and Firefox. But people with 100s of tabs almost universally say that Firefox handles them ok and Chrome fails miserably.
As for Firefox improvements -- FF7 (September 2011) fixed some big memory problems in the browser, and FF15 (August 2012) prevented a very common kind of leak caused by add-ons. But most of the other releases since FF7 have had minor memory consumption improvements. See https://blog.mozilla.org/nnethercote/category/memshrink/ for more (possibly too much) detail.
If you haven't tried Firefox for over a year and you regularly have 100s of tabs open, you should really try it again. If you have an existing profile, it might be worth using the "reset firefox" feature to make sure it doesn't have a bunch of unnecessary cruft in it -- see http://support.mozilla.org/en-US/kb/reset-firefox-easily-fix....
What is Chrome's bottleneck with hundreds of tabs? The resource load from hundreds of processes? IPC overhead for the browser process to managing the content processes?
Memory usage for that many processes. Even with all the sharing it tries to do, its per-origin (there's usually at most one process for each origin, not for each tab) overhead is much higher than Firefox's.
"Was there a particular upgrade that addressed process management and/or memory leaks? I also wonder if it's an OS thing (I'm on OS X)."
I'm on Windows 7, and in my experience the memory issues in Firefox haven't been completely resolved yet (though the Mozilla team are actively working on it). However, as a workaround I have found the Memory Fox add-on useful:
https://addons.mozilla.org/en-US/firefox/addon/memory-fox/
A few versions ago, they added a feature where tab contents are only reloaded on-demand, when clicked. You no longer have a big lag when opening up the browser with many tabs, and memory usage is quite reasonable.
Firefox on OS X is remarkably better in the past year. I ditched Chrome many months ago because Firefox now is better with memory and remaining quick and responsive than Chrome for me on OS X.
A lot of work has definitely been done in the last year. Two years ago, firefox was unusable on the netbook I had at the time, so I used chrome. I think the situation would now be reversed, however.
Was there a particular upgrade that addressed process management and/or memory leaks? I also wonder if it's an OS thing (I'm on OS X).