The Radeon R9 M385 has a faster clock and memory speed but less shaders but comes with more video memory usually (2GB more). If it helps the 8970M would be similar to the R9 M290X. You can't really compare desktop and laptop GPUs against each other since they are designed to work to different requirements.
We can compare tech specs, fps in games and so on. In instance, the HD 8970m is similar to the HD 7850/7870, so knowing it I can look at the different benchmarks and see what fps I can recieve playing a specific game. It's very helpful for any customer. Some people say that m385 is as powerful as HD 7780 so I'd like to know is it true or not.
The R9 m290x is the same HD 8970m with a higher turbo frequency, so these chips are the same.
What chip does m385 have? Tonga or Strato? And what version of GCN is there?