Given the same alignment, the driver with more displacement is capable of more LINEAR output. That's not open to debate or interpretation, it's a fact. It's easily verified with any scientific output testing, always has been, always will be. If you think otherwise, please realize that you are mistaken.
Now obviously that doesn't mean the driver with the higher displacement will be louder in ALL situations and at ALL frequencies, as obviously we can take a lower displacement driver and tune it to a high frequency while we have the higher displacement driver in a flat reponse alignment and get more SPL from the lower displacement driver at or near tuning, but that's about it.
Non linear SPL isn't predicted accurately by linear displacement, because it isn't remotely linear, but when we are talking about linear output, i.e. the only thing output we're going to be using with music, then displacement is still king, assuming you are actually utilizing it.
The RE 8 outdisplaces the DD, thus in a similar alignment, it is going to produce more linear output than is the DD.
