Hi Keith , Im sorry you didnt get a reply / comment on that question and I notice that you still dont have a boat registered in yoiur name so may be still pondering this question . I think Simon is right in that different people have different preferences / requirements .

Interestingly Roger Macgregor played around with various layouts . The earlier 26 S and C were more like the M in layout and `heads ` position but there must have been a demand to have the heads more accessible and hence the 19 and X layouts . The X was popular and ideal for many with standing height heads albeit rather narrow and open cabin , great for 2 or maybe 3 , but the rear berth is rather awkward for 2 people and most X owners have used the V for sleeping and the stern largely for storage .
The M layout was developed largely in response to criticisms of the X regarding Safety and Sailing performance . Firstly on safety there was a case of an X being swamped by a large following sea and then capsizing . I think it was only once and it must have had partial ballast fill to allow this to happen . Anyway there was bad press about it and I believe a requirement that there be a larger step up to get into the cabin . This linked with a desire to better utilise the potentially huge rear berth by relocating the heads forward , which is less of a problem in the higher freeboarded X/M hull .

Regarding sailing there was a view that the X was too boxy and motorboat like and didnt pivot well enough and hence the round of the stern and the switch from centre board to dagger board which can be adjusted in depth without altering pivot point / weather helm . This was probably a false argument since I think the X manoeuvres just as well as the M . The M has a slightly taller mast and a little more fixed ballast and also has the rotating mast and all this means that in the right winds ( and with a good sailor) it goes a bit faster than the X. The mainsheet track on the M is also an advantage in being able to better trim the sail and where necessary create twist to spill wind in strong gusts . The rotating mast is a mixed blessing. It probably adds a little to forward propulsion when going into in a light or moderate wind but it can restrict options for running lines back to the cockpit. However some members have found cunning ways around that .

I have really enjoyed the giant rear bed of the M and the cosy , more traditional feel of the dinette area plus the capacity to slide the galley back to create a lounge effect. Also the visually separated v berth gives additional privacy especially if , as I did , you add extra curtains. The only down side was the proximity of heads to those sleeping in the V but I found a way to reconstruct the door to make it virtually airtight ,which with additional solar vent , improved the conviviality greatly . The fact the heads are not standing height is not really a problem since , after all , most important business takes place sitting down !

The geometry of the M means that there is a little less circulation space and hence the open-ness of the X and the ease of moving from cockpit to cabin suits many who are less agile . On the M however there is greater potential to sleep a larger party in that the table easily drops down to a decent bed and the easily accessed rear berth could even take 3 . ...indeed I think we have two rather packed Ms at the 2021 Chichester big Mac !

Well , thats my pennyworth re Xs and Ms .....more anon....

Roly

PS...you may wish to look at the forum post Rolys Mods ...detailing most of the mods I made to my M plus a link to some photos .