I just installed firefox 15 beta. I have 5 opened tabs and it is using 220MB of ram (no flash apps running) and the plugin container is using 40MB of ram (I only have one plugin installed). And sometimes it becomes unresponsive for a few seconds when switching to another tab. I want to try firefox to see if it has improved since firefox 8, but I think it's performance hasn't greatly improved up to now.
(The computer has 2GB of ram and 2Ghz core 2 duo)
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how does the performance compare to Chrome?
Try using the stable version instead of the beta. They are beta for a reason.