Is that Aurora is considered bleeding edge, which really isn't suitable for production environments. Aurora is quite nice I will admit, but my review was looking for something with more "release-grade" stable code. Aurora is a nightly build which can change as often as a person with mood swings. In other words, unpredictability is not something most of us want to deal with.
Another thing too, Pale Moon and Waterfox aren't allegedly 64-bit... they ARE 64-bit.