The 2 X 560ti's 2GB will be faster than the single GTX 580 3GB.
One card is always the cooler option tho.
Make no decisions yet. Lets see what these new 560ti's with more cores are going to be like yeah?
I have heard that BF3 uses more than 1.5GB of VRAM. In all honesty, I would get the normal Lightning Edition to save $70 but I have heard that games will use more than 1.5GB of VRAM and the extra 1.5GB of VRAM would really help.
I doubt you would notice much with one monitor. If you have future plans to SLi and use two monitors then the 3GB may be useful.
You read that review right? The 1.5GB performs better sometimes because of the smaller framebuffer, not to mention the 1.5GB card runs slightly cooler and uses less power.
That 3GB card is for the extreme overclockers and multi monitor displays. The regular lightning version is no slouch either, it has all the same military grade components just no blue fans that blow reverse for 30 seconds on boot and no dual bios, I believe. I think Guru3D did a review of the lightning xtreme card, take a look at that review when you get a chance and pay close attention to their conclusions.
Oh, I just realised what you said, year over here in Australia the lightning Xtreme is $699 which is a $100 price difference to Newegg. Over here the Lighting is $629. Oh man, prices are hard in Australia. Do you know of a site that sells the Lighting Xtreme Edition at around $600 that ships to Australia or even if it doesn't ship here.