Why did Microsoft choose to change the resources management system from .NET's RESX files?
RESX had useful code generation, providing developers auto-completion for resources names and outputting IMHO very readable code.
The new RESW format is as far as I know, the same bare XML files, but without any code generation, forcing developers to write more code, and depriving them of compile time error detection.
Best Answer
While this article on MSDN doesn't go much into detail as to the "why", it rather explicitly states the "what."
While answering the "why" requires speculation or inside knowledge (my guess is "to save on file writes in the final App"), the fact that the syntax is idental means that you should be able to use whatever tooling you had to create
resx
files to produce Windows 8 compatibleresw
files. (in fact, you may be compiling the resx into resm, similar to how LESS or DART are processed into CSS or JavaScript.)