What does this have that Lastpass does not?
In all seriousness though, Lastpass is not a particularly good looking piece of software, and in small ways that does impact my ability to use it efficiently. It generally looks like 1Password is much better on this front, although I still use Lastpass because it's ~50% cheaper.
Password X in particular is new approach and its first iteration works in Chrome only. Which doesn't mean it will not work in other browsers as well in later versions.