I've been wondering this for a while now. Why would you get a 550ti over a 560se. They are about the same price and both use very little energy. The only reason I can see is the it uses 34w less. I understand the 550ti will fullfill most people's needs for gaming but if you can get a better product for the same price why not?
People who buy the 550 ti are generally not well informed about pricing. They just look at an nvidia card in their price range. Given also how new the 560SE is, it is often overlooked being just that slight bit more expensive.
Most people who research pricing and such generally buy 6850s, 6770s and 7770s.
I don't know... Maybe it's because many people did not research. I always advise people against 550 Ti. I always recommend 7770 instead, or if the buyers really only want nvidia, then I would recommend 560 SE.