For many users, the manufacturer skin (or overlay) UI on a phone is a useful bit of software, adding core functionality to the base Android operating system.
For others, it's akin to bloatware, getting the way of the raw Android experience that they desire.
These phones have been stripped of HTC's Sense and Samsung's TouchWiz, leaving just Android 4.2, or Jelly Bean.
As mentioned before, neither phone is currently available in Australia via the Google Play store, although we imagine that parallel importers will soon find some stock. In the US, the One is priced at US$599, and the S4 at US$649.