Memory Usage Efficiency Benchmarks
IE9 uses the least amount of memory to display a single tab under Windows 7, just under 50 megabytes. Apple Safari comes in second place, using just over 50 megabytes, followed closely by Opera. Chrome places fourth, consuming nearly 65 megabytes, while Firefox uses the most memory (90 megabytes), placing last.
Safari leads in OS X at just under 60 megabytes, followed by Opera at just over 70. Firefox overtakes Chrome to place third by using 120 megabytes, while Google's browser uses the most memory (140 megabytes).
Under a heavy load of 40 tabs, Safari for Windows uses the least amount of memory (just 725 MB). Firefox comes in second at 910 MB, followed closely by Opera at 925 and Chrome at 995. Microsoft's own IE9 uses the most memory (1.75 GB).
Opera is the only competitor to use less than a gigabyte of memory in Mac OS X. Safari comes in a close second, eating just over 1 GB, followed by Firefox at 1.25 GB. Chrome reports a whopping 2.3 GB of usage with 40 tabs open, which is significantly more than any other browser.
I think add ons are much easier to find with FF, and there seems to be a wider variety. Then again I do realize this article wasn't about browsers with add ons.