This is a ridiculously difficult question to answer with such limited information. Even if we had full specs it's difficult to put a number to it because the new GPGPU will have so many new features and the architecture differences mean that without thorough benchmarking, we won't really know how much more powerful it is on average.
So, based solely on the limited information we have I'm going to go with around 2-3x more powerful. It has a more up to date GPU architecture and has double the RAM with the possibility to increase up to nearly 2Gb. That alone would help the console in terms of texture resolution and the extra eDRAM should help with Anti-Aliasing.
The question on my mind is how much of a hit the tablet will have on overall performance.








