Mozilla Firefox for Android competes with many mobile Web browsers, chiefly Google Chrome, which is preinstalled on most Android devices, giving Chrome a much larger market share. That's unfortunate, because Firefox for Android has a number of interesting and unique features, such as support for add-ons, data syncing without a Google account, and the ability to integrate search engines that Chrome won't.
Firefox for Android supports add-ons (aka extensions): Firefox is the only major Android browser we've found that lets you install add-ons, although not all desktop Firefox add-ons are compatible. Admittedly, add-on support is not needed in some cases -- for example, you would use a password manager app rather than an extension. But say you want to download a Flash video over Wi-Fi and then watch it later , rather than streaming it over a 4G or 3G connection and eating into your monthly data cap. Chrome on Android won't let you do that. Chrome on Android also won't let you install the popular HTTPS Everywhere add-on, which attempts to force encrypted connections for increased privacy. And Chrome on Android doesn't do ad blockers.
Custom search engines: Most people will default to Google, and that's probably fine. But if you prefer DuckDuckGo for increased privacy, that's not an option in Chrome on Android. In Firefox, when you go to a website's search function, long-tapping in the search field opens up a menu featuring a magnifying glass with a + sign next to it. Tapping this button adds that site to your list of available default search engines in Firefox. DuckDuckGo is already on this list, so you don't need to add it manually. Unfortunately, you can't quickly swap from one search engine to another, as you can in the desktop version of Firefox, but it's progress.
Data syncing: Chrome users benefit from being able to sync their bookmarks, tabs, and navigation history across multiple devices. You can start on your phone and pick up where you left off on your laptop or tablet. But it turns out that Firefox also has syncing, and it's done independently from any Google service. Using it does mean creating another online account, but Firefox syncing can helpful for people who want to keep their work and leisure browsing separated. This is important not just for privacy, but also for accurately tailored search suggestions.
Clearing private data is all-or-nothing: If you want to erase your history, cookies, and browser cache, Chrome lets you choose several time frames: past hour, past day, past week, past four weeks, and "beginning of time." Firefox only has the last option. You can't just remove the stuff that happened recently. It's probably not a big deal for most users, but it's worth mentioning for those times when you need to correct your search suggestions (or erase some regrettable browsing history). Chrome also tells you how many megabytes of space its browser cache is taking up.
Add-on catalog doesn't filter out desktop-only add-ons: Mozilla's add-on catalog is easy enough to navigate, but we'd like the option to toggle the visibility of items that are compatible with the mobile version of Firefox. It's not an ideal user experience when you find an interesting-looking app but can't install it in the mobile browser.
Firefox's support for add-ons on Android allows you to refine your browsing experience to something meaningfully better than the experience that Chrome -- or any other mobile browser that we've come across so far -- can provide on Android. The advantage is so distinctive that it's hard to make a case for Chrome as your default choice. This edge is softened by the Firefox add-on catalog listing items that aren't compatible with the mobile version of the Web browser, but fortunately the most popular ones usually work on both platforms. Since Firefox is completely free to use (as are its add-ons, though donations to the developers are welcomed), you can judge for yourself with minimal investment.