Dated warscrolls take precedence. So the version in the app is not dated (none in the app are by my knowledge), the one from the tome is. So the way I get it as long as no dated new version is printed, the battletome version is the right one.
Q: If I have two different warscrolls for the same unit,
can I choose which to use, or must I use the most recently
published version? Do I have to use any errata that applies to
the warscroll?
A: You must use the most recently published warscroll
and must use the most recently published errata that
you or your opponent have available. Warscrolls with a
date of publication are always considered to have been
published more recently than a warscroll that doesn’t
have one. If you have two warscrolls for a unit and
neither has a date of publication, you can choose which
warscroll to use
