Wrong
Crossfire creates micro stuttering on the frame rates which will get on your nerves like crazy.
Not an issue with current generation of cards unless you don't have a CPU that can handle the work loads. I don't think you've researched this lately.
The 580 may be slightly more powerful as a single BUT, you'll need two of them or more to do what eyefinity does, which is the only reason you would need a card of that power.
Nvidia has CUDA, 3D, and Physx, while AMD has Eyefinity. Having, an AMD card, I won't disagree with you. However, in order to max games out on a 3 monitor 5760x1080 resolution, I dare say that you're going to probably need a second card to run the games full out without the framerate slowing down. This is especially true of games like Battlefield 3, which is hitting stores within a month. In that respect, I think you haven't thought this through.
Eyefinity is a novelty that very few actually use with only one card. Most people that can afford a good eyefinity/nvidia surround setup can afford a second card.
Older/weaker cards do suffer from this. More powerful configurations don't. Again, you're using an outdated model to make this sort of claim.
If you're going to choose which one, consider monitors. If you want the surround/eyefinity get the 6970, if you want one monitor the 580 will give you the needed power. Just remember that the 6970 is a lot cheaper and when it comes down to a single monitor, you're unlikely to see the difference.
Look at the minimum framerate. The average isn't that much different, but the minimum framerate is about 12 FPS higher average. That would mean that gameplay on the GTX 580 is much smoother, as well as being slightly faster. That steady framerate is very noticeable during heavy firefights.
I maintain what I said earlier. For high-resolution, multi-monitor, multi-card gaming, the Crossfire HD 6970 is the setup to get. Why? It's cheaper and it scales better (more Vram). In the single card, single-monitor sector, the GTX 580 is better. In the triple monitor sector, you need a second card to realize the full potential of most games anyway, so eyefinity becomes nothing more than a perk as opposed to an outright advantage.
I could easily find other examples of this if needed.
