Performance comparison of Wii U is mixed bag
CPU much slower than expected
What we don’t know yet is how much the slower CPU will hamper the development of software for the platform, or if it is possible to dynamically control the CPU clock speed as some have suggested, which could yield better on-demand performance, but we doubt it.
The decision is clearly a money saving move by Nintendo, and so far we have not seen anything that makes us think that the system is hampered by the choice in a very negative way. So far, the CPU appears to be up to the task, but long term evidence suggests it could struggle.