Well, I guess it always depends where you look and how they test it.
It might be that the "performance for usual tasks" also took in account the faster RAM speed, GPU speed, other CPU extensions that speed things up, etc. rather than the raw CPU power.
I don't remember exactly where I read that, but it was a while ago.
Here's another estimation:
http://www.phonearena.com/news/ARM-Cortex-A15-a-deeper-look_id36225
The relative performance of an A15 is 6.13 times as fast as the the A8 (the one in the Classic and Rebirth Pandora). I don't know exactly what the relative performance is, I guess it's a mixture of the performance combined with the power usage, as the A8 with a smaller node has a higher relative performance (and we know it uses less power for the same tasks).
Does that mean that an A15 core is 6.13 times as fast as an A8 when using the same power?
I can't imagine that as well, as it would mean the Pyra would have a battery time of 60 hours when running at the same performance as the Pandora runs, and I certainly can't imagine that.
So not sure where to find proper informations here.