Dual screen ultrabooks vs surface pro + keyboard case - Which is better?

So we have probably all seen the samsung concept of the dual screen ultrabook/tablet here:


and of course the surface pro here


What do you think would be the better form factor?

We don't really know how the surface keyboards perform yet, but maybe a dedicated ultrabook keyboard will still feel better, if so would that be worth the sacrifice in size for a thicker dual screen display? Would you prefer one of those convertible devices that uses a single screen that slides or twists or detaches? I tend to think the dual display form factor is more streamlined because there is not so much attention to docks or added twists and degrees of freedom for something to break and go wrong. It literally doubles as both an ultrabook and tablet at the same time by simply sticking a screen on the lid.

One thing that worries me about a dual screen ultrabook is that it's hard enough for manufacturers to put ONE good display on their machines, if they add two maybe both will have corners cut to save on costs.

Opinions? I honestly don't know what the best form factor for microsofts dream of a laptop/tablet will be.