^I think you're right... judging from everything that I've heard/read, the 7990 is just a hair faster than the GTX690, but sucks quite a bit more energy and is quite a bit less efficient. I don't think it's double the wattage, but it's a significant amount.
If power usage and efficiency aren't issues for you, then the 7990 is marginally faster; if they are, though, the 690 is a better choice.
Found it. Read that entire article and you can draw your own conclusions.
The '7990' has a very slight performance edge, but the 690 is a more well-rounded card better in basically all other areas (noise, efficiency).