From what I've gleaned GK110 and Tahiti allegedly have similar DGEMM/peak ratios in the 80-85% range, with Tahiti just shy of 800 GF and N20 somewhere north of 1 TF.
Tahiti as we know it has a TDP of 250W, and some Tesla cards are in the same area, so I'll just say they're equal in a hand-wavey way for now.
Giving N20 the benefit of the doubt and saying it gets around 1100 GF as opposed to 1001, that gives N20 more than a third more DP FLOPS/W.
The perf/watt argument can override price if there are restrictions in density or operating budget due to power and cooling.
On a one to one chip basis, that puts N20 at an advantage in DP in terms of peak and power efficiency. The equation does flip if SP is involved. (hence N10, possibly)
The software and features argument could override both price and power. I'm curious what AMD can really offer over N20 in this time frame. There is at least the perception, and anecdotally some very negative ones at that, that AMD will need to overcome an "it's AMD" disadvantage as far as the GPU compute side goes.
