Originally Posted by
Rafax
Look the first 6 on the 660ti refers to its generation, one generation ahead of the 580, the second 6 on the 660ti would be something like performance tier which goes like this 660>660ti>670>680>690, and for the past generation its the same thing but with the gen number being 5, the higher number only counts if its the second one and not the one refering to the generation of the card, a 580 is a top end card from the las gen and the 660ti is a mid end card from current gen so it actually means that the 580 might score better in synthetic benchmarks like that but it will be very close in game wise.