These are very different speakers! I suspect personal preference will dictate which one you would prefer.
I've listened to both and own the 1.3SE. In my view, the M20s have a more forward presentation with the top end being a bit too hot for my ears. I auditioned the M20s perched on their factory matching stands and an all Classe system. IMO, the M20s would be better matched with tube equipment but I haven't heard them set up this way.
The Dyns have a smoother top end but I didn't sense a loss of detail compared to M20's metal dome. The Contours also have a fuller/fleshier mid range presentation which I prefer, specially on vocals.
The M20s were the last stand mounter on my must audition list prior to my purchase. I believe that if you were to spend time with both, the decision would not be too difficult.
Jet