Oban was the codename for AMD's chip for the nextbox a while ago. Hmm.
Charlie at SemiAccurate released that information. Since his article that Oban taped out Dec 2011, we now know the AMD-Microsoft project name is Kryptos and the PS4 project name is Thebes. AMD is using Greek names from Mythology for their GPU family and Console project names.
Oban is not a Greek name, it's either a city in the UK with a Scotch also named Oban from that region or a
Large blank Japanese gold coin with bumps. Oban probably describes the interposer that both Kryptos and Thebe will use. Further Kryptos is hidden in Greek and likely Thebe is the custom APU part that contains hardware that both will use. Kryptos besides containing Thebe also has features to support serving Media (DVR & more) to handhelds. In this speculation a second GPU for both is likely either discrete or also on the same transposer sharing the same memory. Microsoft trading a few CUs of die area on the GPU for the extra circuits to support serving Handhelds.
The above is speculation but it explains a number of issues that have been raised since Charlie's first article.
I think both are targeting a console with as low a price as possible < $399 (less than) including depth camera. Both will have Skype and both will have a common standard for gesture controls. For developers and brokered by AMD, both will have APIs that are very similar.
For the Xbox 3 rumors have 12 CUs for the second GPU to the PS4's 16 CUs so Xbox 3 will have total 14 CUs to PS4's 18 CUs.