Which graphics card is best: Nvidia GTX 550 Ti or Nvidia GT 610 galaxy

The stronger card is going to be the 550Ti 10/10. The Nvidia cards with 2nd numbers in a series that are 1, 2, 3, or even 4 are meant as home theater cards and will not be worthwhile unless those are the only things you are trying to accomplish. I would say the 7770 is the best value as well.