SafeZone cannot reuse already installed user's webbrowser and modify it - it'd be most elegant (user can continue using his web browser s/he's used to it), but it's not safe. Finally, we could choose only between FF or Chromium engine. I'm a FF guy, I love FF and use it. Opera isn't also bad at all - my gf uses it so do I (unfortunately it's not open-source). Chromium is huge project, its source code is written very well - something what's not seen so often. We modified Chromium web browser, removed some problematic parts (e.g. autoloading of some plugins, ...) and we plan to implement other security plugins after v6 release when we get more time - and thus, Chromium was the evident choice.