I switched back from Chrome to Firefox yesterday, opening every URLs and so every tabs opened in Chrome, spinning every tabs spinned in Chrome, and so on. 30 tabs in 2 windows, with the same set of extensions, with the standard theme and I checked the number of file descriptors — as older versions of Firefox were not using too much memory but a very high number of file descriptors — and the RAM.
The results, about three or four checks: Firefox does not use too much file descriptors, which is a good point — the two browsers use the same amount of them —, but consume now far more memory than Chrome, from 3 to 10 times, depending on my tests.
By the way, may be it is the cost to be paid for a faster display, I don’t know, but it’s at the expense of other opened applications!
A little point I also note: the combobox (dropdown lists) are still awful in Firefox, comparing with Chrome, at least on OS X!
Nice try Mozilla, but you can do better!