Due to the native navigations, the location of the NEXT (or BACK) buttons would depend on the OS they are running on.
On iOS, it's common to see the back button on the top bar, and users are very used to this. On Android, it's mostly at the bottom of the screen.
On another note, based on the images above, the large next button at the bottom is only viable with application interface that needs the user to go NEXT, like a payment screen or a registration page. It serves more as a guide than a navigation.
If the user has to consume a large chunk of content on the page, it would make sense to only have it on the top, as a nav. However, if you are sure that users will somehow consume all the content in a very short time, you may provide the large NEXT on the bottom.