For what it's worth, one fact and an anecdotal observation:
One fact: Currently, Chromium-based browsers suffer from a nasty memory leak: each time one bring up an extension's popup UI, a big chunk of memory is leaked.[1] This alone for me justify using Firefox over Chromium if one has an extension which popup UI must be accessed often.
Anecdotal observation: I have noticed since a couple of versions now that it appears Chromium's garbage collector can be very lazy sometimes. To the point where I am wondering if this is a bug, because the memory would just not be reclaimed by the browser until I forced it through the developer console: upon clicking the trash can in the Timeline tab, 60 MB were re-claimed for one of the extension (from ~130MB to 70MB). This was after waiting for an hour to see if it would be reclaimed. Yes, there was a lot of idle time while I waited.
One fact: Currently, Chromium-based browsers suffer from a nasty memory leak: each time one bring up an extension's popup UI, a big chunk of memory is leaked.[1] This alone for me justify using Firefox over Chromium if one has an extension which popup UI must be accessed often.
Anecdotal observation: I have noticed since a couple of versions now that it appears Chromium's garbage collector can be very lazy sometimes. To the point where I am wondering if this is a bug, because the memory would just not be reclaimed by the browser until I forced it through the developer console: upon clicking the trash can in the Timeline tab, 60 MB were re-claimed for one of the extension (from ~130MB to 70MB). This was after waiting for an hour to see if it would be reclaimed. Yes, there was a lot of idle time while I waited.
[1] https://code.google.com/p/chromium/issues/detail?id=441500