No matter how you look at it, the browser ranks among the most resource-intensive processes on your machine. Why? First, a web browser is not a document viewer and a website is not a simple document. Browsers are complex and full-blown programming environments. Technologies such as HTML5, JavaScript, and Flash are hugely more powerful and complicated than any document. They're running code! It's no wonder browsers require lots of CPU time and memory. It's a question of what has less impact on your system:

Again, the more memory your browser takes up, the slower it will go, and it will affect the performance of your other applications as well. Plus, keeping your hardware busy means a decrease in battery life on notebooks. Keep in mind that Chrome, Firefox, and IE9 are built as basic 32-bit applications. This restricts them to 2 GB of memory, which increases the chances of reliability issues and freezes. (You could use the 64-bit versions, but these are incompatible with many add-ons.)

Among aspects like security, usability, stability, and compatibility I'd rank memory usage as one of the more important factors when deciding between browsers, as it affects not just browsing speed but reliability as well as overall PC performance.

To determine the memory usage of browsers, I prepared the following scenario: