Well if it's to compare like this,
DS > PSP
Wii > PS3/360
3DS > Vita
Then you look
PSP > 3DS
PS3/360 > Wii U
like that i assume that Wii U undoubtly it's more powerfull than PS3/360
About the next gen winner, it's to soon, but i think that on home console market Sony will take the sales crown, about overall quality winner i don't know.