Harbeth 40.3xd vs Graham LS5/5

Haven't heard, but interested in what responses you get.
I'm drawn to the looks of those slotted apertures on the LS5/5 and wonder if the theory behind them works(?).
Though I'm not in the market for another speaker the LS5/5 is weirdly desirable to me as an historical curio alone. 

Looking at the graphs in the BBC paper there doesn't appear to be any advantage to using the slot for the bass driver when utilised in the 3-way design(?).
Hard to tell from the graphs if there is much advantage to using the mid-slot either. 
Anyway I suppose the proof is in the listening.
Looks like Graham must have done away with the 4db bass boost via preamp EQ with their iteration.
The design does look very retro-cool though.
Will be interested to hear of any comparisons to the M40.