If you take a closer look you'll find some differences. The clock rate is the most obvious, but I wouldn't pay too much attention to that. The effect is most likely a single digit number somewhere in the 150 FPS area where you can't tell any difference anyway.
The power consumption is interesting. One might suggest it would be related to the clock rate but it isn't.
All in all there's not that much of variation in the numbers that I'd call one "good" and another "extreme".
The main differences seem to be in 6 or 8 pin connectivity and physical size. For upgrading an older computer the short 6 pin version sounds like a tailored alternative, a new build usually has both space and connectors for the two fan 8 pin versions.