Vita still has a big lead over the Wii U and outsold Wii U last year despite the latter having overly hyped games like Pikmin 3, LOZ: WW HD, Wonderful 101 and SM3DW versus the Vita's KZ: MC and Tearaway.
Even this year Vita had o big release and for the time being stil has outpaced Wii U despite Wii U getting games like DKC: TF.
However now it seems likely the Wii U will outsell it by the end of this year but it is happening after Nintendo launched nearly all its popular franchises on the Wii U compared Sony just launching one of them at launch which wasn't even that well recieved compared to previous installments.