Afaik the best predictor for ETH hashrate is memory bandwidth. AMD's latest generation of GPUs actually employs a large on-die cache combined with slower memory

Afaik the best predictor for ETH hashrate is memory bandwidth. AMD's latest generation of GPUs actually employs a large on-die cache combined with slower memory compared to the 5000 series (and the NVIDIA 30 series), resulting in a naturally lower hashrate.