As of February 2012, Firefox and Chrome are neck-and-neck in the race for being the most popular web browser in the world, both with about 36 percent market share, according to statistics from W3Schools. While Firefox claims a slight lead over Chrome in terms of popularity, both browsers offer features that make them worth taking for a test drive. Important factors such as speed and security are more ore less comparable for the two browsers, so your ultimate decision may come down to which one offers the customizations or features that you need to perform your desired tasks.
Structure: When it comes to structure, Chrome and Firefox ascribe to two different schools of thought. Firefox, owned by Mozilla, is an open-source project with many contributors, whereas Google's Chrome is closed-source and documentation is kept private. That's not to say that Google doesn't invite open-source projects; but its open-source browser is Chromium, not Chrome. What this means for the browser experience is that Firefox has potentially had "more cooks in the kitchen" working out potential bugs. Behind the scenes of the two browsers are two different browser engines -- which handle how the browser manages your requests; Firefox relies on the Gecko browser engine, while Chrome is based on Webkit. While both are equally viable, Webkit -- also used in Apple's Safari browser -- is more often used in mobile devices. For the future of browsing, this may be a big factor in overall viability. Firefox is also available on more operating systems, including Mac OS X, Linux, Windows, Sun Solaris, Open BSD and Free BSD. Chrome, meanwhile is available only for Linux, Windows and Mac; other operating systems must use Chromium.
Security: An important aspect for any browser is its level of security. According to a study conducted by Accuvant, Chrome emerged as the most secure browser, over both Firefox and Internet Explorer -- with Internet Explorer coming in over Firefox. Chrome scored the highest marks for having the highest number of anti-security measures. While both Firefox and Chrome employ"sandboxing" to isolate potentially harmful attacks on your computer, Chrome employs it more often, for more processes. Likewise, Chrome offers more security features for plug-ins, and automatically disables them when they become out-of-date.
Extensions: When it comes to extensions to the browser, Firefox is the clear leader in the number of options. Likewise, Firefox comes with a number of extensions already built in, which could lead to a slower initial load time for the browser. If you're looking for the fastest load time, Chrome may be your choice. If you want a wider array of features to add in to your browsing experience, Firefox may be the answer. At present, Firefox's extension options include more security add-ons than Chrome. And since Firefox has been around longer, there's also been more time for finding and solving security issues.
Tabs: Another distinguishing feature of Chrome is its separate processes for each window and tab. When you open a new tab or window, Chrome separates that tab or window in to its own process. What this means for you is that if you're experiencing a slow load time on one site, it's not going to slow down your experience in other windows and tabs. Likewise, if one tab crashes, it won't crash the entire browser. Firefox, meanwhile, continues to employ the more traditional method of processing tabs, in which are all are tied together. In terms of security, this process separation employed by Chrome may make it more secure overall.