@smashman42 @_08's app currently has more features (horizontal scrolling mode, manga support, etc.); and at least until I do the next release fewer bugs. I'd say has a more "androidy" look and feel, mostly due to differences in the used framework.

I guess they both were born out of dissatisfaction of their respective authors with the official app, and gain features when someone requests an addition, or whenever the author feels bored ¯\(ツ)/¯.