The delta between the One and 4 GPUs seems to be 0.6Tflops, or 600GFLOPS (I'm ignoring this 10% thing because we don't know if the ps4does the same). That would be on the very high end of estimates for the Wii U GPU. Most are around 300-500 I think. I believe the median guess would be around 350 for the Latte I would assume, most people saying 300 and some going way higher.
There's also the low-end estimate of 160 ALUs. Which coincides with claims by developers that it's worse than PS360 in shader throughput. I've heard that EA pegged it as 90% of a PS3.
There will be some OS GPU reservation on PS4 since it will have to draw to the screen intermittently and unpredictably. Although something like 10% seems excessive for overlays like notifications.