I know, just humour me
Well it looks like the XBONE has a GPU with 12 compute units providing a total of 768 threads at 800MHz, with 16 ROPS for a total 1.2 teraflops but clockspeed is not confirmed as yet. Looks to be around the power of a 7770 With a lower clock speed and less ROPS.
As for the PS4 its stated to have 18 CU, 32 ROPS something like 1154 threads at 800Mhz for 1.84TFlops, slightly more than a 7850.
Both the XBONE and PS4 GPUs are supposed to use a newer GCN so they have increased efficiency compared to their comparable PC part.