Hema Maps app has gotten me from edge to edge of this continent a few times. The 250k is government data, what is valuable is the work on the ground Hema has done for their own maps. That stuff is updated every couple of years, especially the high traffic places like the Cape/ Kimberley.
The new Explorer app is different. It ties in weather, camp spots, satellite view and topographical data with the same suite of Hema maps. It's moving towards a unified product with everything in one app you need for touring. I haven't tested it out extensively in the field yet, but from what I've seen, it's the future.
Carlisle