Now that Chrome seems to be getting a bit more bloated and Firefox seems to be tightening it's belt, things will probably begin to even out.
In my experience, IE is losing bloat, Chrome started with a bit of bloat but quickly lost it, whilst Firefox has had bloat for a while.
[1] https://groups.google.com/a/googleproductforums.com/forum/#!...
[2] http://techpp.com/2011/09/28/chrome-14-vs-firefox-7-memory-f...
[3] https://blog.mozilla.com/nnethercote/ talks about it frequently
What counts in the end is speed, security and api's.
Interestingly, however, when Flash crashes on one tab it crashes on all of them.
I've recently switched back to FF and found that it worked in the places that Chrome didn't.