Why is your Bitcoin mining benchmark so screwed up? You don't say which miner you used, and what arguments you gave it. Also, DiabloMiner seems to function fine on 79xx, so why didn't you use that?
People who gripe about effeciency have a legitmate logic behind their gripes (Electricity bill costs). Problem with the logic is that comparing equal-level GPUs from both ATI and Nvidia (Say GTX 590 vs HD 6990) the overall difference in wattage is extremely small. Both cards are gaming GPUs and power hogs. When you find the difference in wattage when running them at load in games for 12-16 hours a day at worst case scenario over the corse of 30 days (one billing cycle), the difference in power bills would is less then a couple bucks at most.To say no true gamer cares about effeciency is false.