Still, you can see that this particular game IS very memory intensive, because on other games, with similar settings, the GTX580 trounces the HD5870. Then, I still think its NOT a good term of comparison, which was my stance after all.
No it wasn't, your original stance was:
This is no better result than an HD5870 with 2 GB RAM, according to the HardOCP review...
Which is not proven AT ALL.
Besides, at 1920x1080, the cards might not be memory limited anymore, and so the advantage of 2GB vs 1.5 GB might not be so pronounced - I bet the 5870 2GB in 1920x1080 falls far lower because it no longer has the 512MB advantage and now falls behind in actual speed. But unless someone has a comparison at 1920x1080, all we know is that:
at 1920x1080, the F1 results favor the 6970