The bigger question, I think, is whether it's still 2nd gen GCN (1.1) based, or is it 4th gen GCN / Polaris all the way. At least display controller and UVD should be from Polaris
If it's Polaris, it would be faster even at identical clocks [in many cases]
Memory compression.
Primitive discard accelerator.
Should offer perf at the same clock.