Thanks for the replies. Regarding the video link, no fps display is shown, making comparisons difficult. In Second Life, the killer is displaying crowds of avatars in areas with lots of scripts. The video shows only one avatar in low lag areas.
Here is a link to the only benchmarks I have found for Second Life, I do not know where it originally came from:http://community.secondlife.com/t5/Second-Life-Viewer/What-video-card-do-I-need-for-SL/td-p/1546603
It shows the gtx550ti outperforming the more expensive hd7970. This has been the experience of two people I know personally, a low level nvidia card working better than a high level Radeon card.
For whatever reason, nvivia still seems run SL better than Radeon, so I got a gtx550ti.