As someone noted Aurora is simply an alpha of a future version of Firefox. Instead of using Aurora you can just simply wait for a couple of months, and Aurora will make its way to beta, then to stable release. Chrome and Firefox both have a process like this:
Firefox: Nightly (3 versions ahead) -> Aurora (2 versions ahead) -> Beta (1 version ahead) -> Stable (current version everyone is using)
Chrome: Nightly (3 versions ahead) -> Canary (2 versions ahead) -> Beta (1 version ahead) -> Stable (current version everyone is using)
The further ahead you are the more likely you are to have stability problems and crashes, because it's pre-release software. However you can get to play with the bleeding edge features, and also sometimes they're faster. For example I was in touch with Mozilla recently and they've added a performance improvement that helps speed up Construct 2 games in Firefox 12 (currently Aurora). That's why it'll be faster - it should be about equal with Chrome. If you don't want to install Aurora, you can just wait for Firefox 12 to get released :)