From what I hear (and I trust my source on this as reliable), the CPU chip in WiiU is almost certainly weaker than Xenon & Cell. Which is why some devs have outright refused to port their existing (in-development) PS360 games to it. I believe Nintendo indended the GPU compute support to make up the difference for their weak CPU choice, however the CPU performance is so bad that devs would be required to refactor their entire engines to get stuff working on the GPU instead, and for many dev that would be impossible on their current project schedules.