I've been at home marking all day today. I've spent a bit of time listening to both systems: Devialet/Vivid V1.5 in my study, and Magtech/ML Montis in the living room.
Despite the excellent amplification of the Devialet and the wonderful clarity of the Vivids (they really are very good!), the gap between the two systems is very very big. I'm trying to put my finger on exactly what separates them and what makes the MLs so wonderful, hence the following ramble.
The FR of the Montis may be no better than other similarly priced speakers. It's fairly flat from 20kHz down to 30Hz, but nothing special. FR certainly doesn't explain what's going on.
In terms of dynamics, the Montis go very loud without distortion. But again that's what you'd expect of speakers in this price bracket. I do think there's something about the dynamics of the speakers that's special though. And I suspect it has to do with the shape of the dynamic "envelope". Think of cars. A BMW 320i and a BMW 335i might feel pretty much the same cruising at 50mph. But the 335i will get there quicker; its acceleration is superior. In the same way the MLs accelerate to the desired amplitude quicker. The dynamic envelope has steeper slopes or a faster "rise time", if you like. As a result the music has more drama; the separation of different dymanics is clearer. I think this is one aspect of the magic of panel speakers.
The other aspect has to do with the soundstage, and specifically the separation of instruments. I've heard speakers that do a better job of lateral separation. The Devialet Phantoms are a good example, with their concentric HF and mid-range drivers and the bass drivers right behind them. They're one example of a (nearly) "point source" speaker. I'm sure the KEF Blades or big Tannoys would be at least as good at lateral separation. The lateral separation of the MLs is pretty good, but they bring something quite new to the party. The frequencies down to 340Hz are evenly spread over a vertical array five feet tall. What this means is that there's a vertical dimesion too. And somehow the vertical dimension makes the cues in lateral separation easlier to hear.
I hope that makes sense. It's the best I can do right now. And I hope it gives a sense of just how good the speakers are. They should be on everyone's to-do list.