Avatar system will be more advanced than on Wii
However, the Mii system on the 3DS is slightly different than on the Wii, which means users cannot trade their virtual self back and forth between the two systems.
The reason for that is Nintendo wanted to enhance Mii customization and connectivity, so 3DS Mii characters are more advanced than those on the Wii, and because the Wii's firmware upgrade capabilities are highly limited, there's no way to put them on the system.
That won't be a problem with the Wii U, according to a report from IGN.
The site quoted Nintendo producer Katsuya Eguchi as saying, "The Miis that will be used on the Wii U are going to be the same as the ones on the 3DS."
He spoke in the future tense because as of yet, that feature hasn't been implemented in the Wii U development tools. As a result, anyone working on a Wii U game that will incorporate Miis hs to work with the regular Wii Mii tools.
This led to some confusion at E3, since the prototype games with Mii characters looked exactly like those from the Wii, as opposed to the enhanced Miis introduced in the 3DS. That was just one of many things that created confusion over the Wii U and caused an unexpected dip in Nintendo's outlook after the new console's unveiling.
However, when the Wii U does actually become a reality, that will change. "We added some features, and the Mii editor that's on the 3DS is different from the one that's on the Wii. Ultimately we'll use those same Miis on the Wii U," said Eguchi.
Eguchi also said Nintendo is working on connectivity with Miis between the 3DS and the Wii U, but nothing has been confirmed and he did not elaborate on details.