Someone compared the memory usage of Microsoft and Mozilla's upcoming browser products – IE 7 Beta 2 and Firefox 2 Alpha 1.  

It's certainly not a scientific test but as far as I'm concerned, the results are fairly valid. One thing which is quite surprising is that Firefox actually uses less memory than Internet Explorer. Firefox has acquired a bit of a reputation for being a memory hog by some over the last few months; this test proves that Firefox isn't much worse than IE. 

I wonder if the fact that IE7 is finally separated from Windows Explorer means that Internet Explorer's memory usage will be reported more accurately.

One thing which is worth noting is that the test was carried out with bfcache disabled in Firefox. 

Browser memory usage is certainly worth investigating more.