Windows Mobile has not had the ability to handle OOXML-based documents until now.
This might make 2 applications which are built from the same codebase and properly support a derivate of OOXML. Both applications come from the same company, to whom OOXML is "a simple matter of (its) commercial interests", according to its own manager.
A choice between "masters" (or "master race") is a false choice that results in mass exploitation and ultimately eradication (when there's little left to exploit)