I use both, I find Firefox handles things like java and flash better than Chrome
thing is, both of these are severely outperformed by HTML5 and they require the user to install their stuffty plugins.
on the subject of the topic, Chrome requires that extra memory to keep every tab in a separate process, so the entire browser doesn't forget over when one person's website doesn't do what it should.
go with chrome if you have the memory, firefox otherwise.