I reckon it will surpass both the Xbox 360 and PS3 in performance, judging from the specs that have been release, the GPU is the best part about the system.
Xbox 360 GPU - Xenos based on the X1900/X1950 PC gpu's
PS3 - RSX based on the GeForce 7800 PC gpu's
Wii U - judging from released specs its based on the Radeon HD4800 series PC gpu's
Now to me that equals pure win, hopefully it should have decent RAM and a good custom IBM CPU to back it up...^_^