I recently got Minecraft for the WiiU and shortly after there was an update. I have searched the wiki as well as extensively googled and have not been able to find a change log or update notes etc. . All the sites link to a change log, but only for Xbox and PS4 and then say WiiU will be updated later. But I already have updated and don't know what was changed. I haven't played much at all prior to the update so I have no way to compare features either.
While the minecraft wiki doesn't have too much detail on the changelog/updates at the time, you can find (at least the recent) patches/change logs on the minecraft forum.
Here's one link that I found on the minecraft forum - Minecraft Updates/Change log - WiiU edition