Drivers are pretty much hit or miss from both companies with some pretty gnarly results. I think if you plan on going multi-card the scales would tip towards NVIDIA, but it doesn't seem like you are. In either case, if money is no object, the 580 without a doubt (fastest card out there). If money is a factor, 6950 2GB, it's been the best bang-for-your-buck for about a year.
Why would you say NV is superior with SLI? I dont see it from both companies record, they are doing ok for the most part.
They have had plenty of issues recently as well. AMD messed up with CF for Skyrim (which can be fixed via user tweaks or 3rd party software), thats about it. BF3 has great (better) CF scaling. Rage did not have CF support and did not need it given its 60 FPS cap, but it was fixed relatively quickly.
DA2 was a AAA title that sucked on NV hardware with crashes, texture bugs and no SLI support for a month. There's a huge thread on it here. So if we look at recent history, both companies have messed up but its an exception, for the most part, CF/SLI has been performing very well.
Overall, current gen AMD cards scale just as good or better than SLI. I don't see justification for your general statement.
OP: For 1080p, 1.5gb vram is fine and gtx580 are great overclockers compared to 570. Buy according to your budget.