Fair enough, you should stick with nvidia if you have had a better experience with them.
If your thinking about sli, then definitely go for the 2gb ones. I know it's in reference to the 2gb 6950, but the same applies for 2gb 560's:
'Also, you must consider multi-GPU configurations. When running CrossFireX or SLI you want the most RAM you can get per GPU. If not, you will have this awesome powerhouse of an engine being held back by small cheap tires; your ultimate gameplay will be held back. Spending a little bit more and getting the HD 6950 with 2GB will give you the headroom to setup a fast CrossFireX configuration that will allow high resolutions with AA that won’t be held back by the memory.'
http://www.hardocp.com/article/2011/02/24/amd_radeon_hd_6950_1gb_performance_review/4