Honestly, I really don't think that Playstation home was copying the Mii system from the Wii ... It is clearly a "copy" (for lack of a better word) of Second Life.
At the same time, I think Nintendo didn't put much thought into Miis ... Nintendo started working with Mii like avatars in the days of the NES/SNES, probably had 3D versions of them for the N64 or Gamecube, and they probably were using this simple avatar system to rapidly prototype games that used the Wiimote. I think they added them to the console by default because it was kind-of fun to create them, and the developers liked seeing what others had created being imported into their games. I could be wrong but I think Nintendo put more focus on Miis with the 3DS and Wii U because of how popular/successful they were with the Wii.







