Chrome is often much faster for me at rendering pages also, and I even get occasional hang-ups with FF where it just sits there for a moment, and that rarely happens with Chrome.
Speed test sites rely on Flash to generate the cute graphics so that could be a difference, but I wouldn't think it's real, as far as actual computer-Internet bandwidth. It's a browser/display thing.
I just ran both on www.speakeasy.net/speedtest
- New York server and got 25.65 with Firefox and 25.72 with Chrome, so it is faster - LOL...not that you'd ever feel the .07MB/sec! So, my assumption is that unless the browser is an active participant in the packets of data flying back-and-forth that comprise a speed test, Firefox isn't really showing your true performance.
Now, that is definitely not saying it isn't significant, in fact it suggests that FF is indeed slower in at least that one task, and that you might want to use the two browsers selectively and judiciously - where it doesn't much matter or when it performs okay, grab the Fox if you like its interface and the extensions you've got installed, but when it does matter or if you experience a slow-down or hang-up, reach for the Chrome.
In any event, Web browsing is only one facet of the Internet, along with e-mail, FTP, SSH, VPN or whatever else you might be running, and with those services I'd assume you've got use of your full actual bandwidth.