When comparing the Reference design, against the EVGA and PNY cards, you will find that all three cards have the same base clock of 1440mhz, both the reference design and the PNY boost to 1710mhz, and the EVGA boosts to 1755mhz so the EVGA card boosts higher, but by less than 4%.
If the price difference for the EVGA is more than 4% over the cost of the PNY then I would say the EVGA is overpriced, but it's not just about the performance, some of us will pick one over the other based on other factors such as the look of the card and length of the warranty or quality of the support offered by the manufacturer.
Assuming that performance scales in line with clock and boost speeds, if the EVGA was producing a 4% difference and you were getting 200fps with the PNY, that would mean that you would get 208fps with EVGA, but this assumption is wrong, performance doesn't scale in line with the clock speed alone.
I found this
comparison between the EVGA and PNY, and found that the EVGA is only just a bit better than the PNY.
If you look through the comparison you will see that the EVGA has:
- 3%-4% greater floating-point performance
- wins on pixel rate, texture rate, and GPU turbo speeds
- both cards achieved the same 19000mhz effective memory speed
I see no compelling reason to pick the EVGA over the PNY other than availability, as the differences are quite small, and you might get lucky with a PNY that performs better than the one used in the tests on this comparison, or if you're unlucky you might get an EVGA that performs below the PNY levels, it's all down to the silicon lottery as not all chips are created equal.