I use both browsers. Chrome for instabrowser (Firefox can take a minute to load sometimes >_>) and Firefox for main browsing when I have tons of tabs, I have a really handy extension called
MileWideBack that's the biggest reason from keeping me away from using only Chrome. I'm hoping Firefox 4 will make me come back to one browser since having seperate histories is annoying when I'm trying to find a page.
This addon might help to lower resources use.
Memory Fox
Lowering the number of addons you use will also speed up the browser.