The Jaguar outperforms Cell in most things, except for brute force floating point performance. Aside from that Cell in its PS3 version has tons of issues.
As for the Wii U CPU, even if it's unchanged except for the Cache, the PPC core itself still isn't actually bad. But with three cores and just 1.2GHz it's to slow.
Would've preferred a 1.6GHz quadcore. A modern x86 still would have been better than the old 750, but Wii U would have much less issues even with a faster PPC.
That said, if you go and cdompare different systems, Wii U and PS4 have an audio processor. PS3 had to do all audio stuff on the CPU.
Wii U and PS4 are intended to do more on the GPU. Stuff that was intended to be done by the CPU on PS3.







