I compared Firefox (3.5.9, with all my addons) and my Opera Portable Browser (10.51).
Tested with the same amount of tabs.
BROWSER--------RUNTIME--------feeled SPEED-----------RAM-USAGE
Opera--------------3hours------------FAST--------------------76 MB (24 MB minimized)
Firefox---------------3hours------------SLOW--------------------226 MB (mimiz. same,4h~413 MB)
Chrome-------------2hours------------FAST---------------------369 MB (mimized not much difference)
Internet Explorer---2 hours--------DECENT------------------496 MB (mimized not much difference)
The conclusion:
Opera seems to be very fast and stable, even several windows with tabs do not brake the stability.
The Ram-Usage is outstanding and fits for general surfing and also power using.
However, Firefox is still my prefered browser because it has too much addons which I would miss on others.
I will also test chrome and the Internet Explorer in the above chart.
This will be added later on...
EDIT: Sorry I twisted opera and firefox in the ranking, changed it.
EDIT2: Chrome is using different Processes, as shown in this screenshot..
http://img651.imageshack.us/img651/1772/chrome001.jpg
The Firefox Ram-Value highly increased after the 4th hour of usage, it feels like its getting slower.
The Chrome RAM-Usage is also very high, but the single processes are not a good indicator for getting results.
At the top of the Top is the Internet Explorer, it uses also different processes for each tab (like chrome), but its RAM-consumption is the highest.
EDIT3: Mozilla announced that they will also use in future releases several processes for each plugin.
The feature is called 'Lorenz' and will enhance the stability and browsing speed.
For further information check this link.
The latest version which includes this feature is 3.6.4 Beta