Oddly, Nintendo has never released official specs for Wii U. It is theoretically improved over the Xbox 360, equipped with "an improved, more modern AMD Radeon graphics core, twice as much RAM available to developers."
While games will undoubtedly improve as the console matures, a look at the Wii U version of Call of Duty: Black Ops 2 shows that there may be one weak link in the console's design: the CPU.
The Wii U version of Black Ops 2 is essentially a straight port of the Xbox 360 version, down to the identical 880x720 resolution and 2x MSAA. "Aside from gamma issues, we're essentially looking at exactly the same presentation," Digital Foundry noted. In fact, the Wii U version looks better than the PS3 version, which the analysis described as "compromised."
However, the framerate struggles on the Wii U version, dipping to about half of what the Xbox 360 original can handle. Admittedly, this is a quick port on new hardware, which should account for some of the performance loss. However, Digital Foundry believes that the system's CPU is its "main bottleneck," especially when "bearing in mind the specific areas that are causing the most noticeable dips in performance," specifically "any scene where a lot of characters are in the area."
Future games on Wii U will undoubtedly perform better as the console begins to mature and developers get a better grasp on how to best harness its abilities. However, much like multi-platform teams struggled to deal with PS3's unique Cell architecture and divided memory allocation, developers will have to balance Wii U's beefier GPU with its apparently-underpowered CPU.