Motul makes a huge range of oils and many have overlapping characteristics. The Motylgear range are highly technical synthetic oils and no doubt very good but they do not claim it reduces noise. I have had no experience of them. The Motul Gearbox http://www.motul.com/it/en/products/113 is a mineral oil that has a molybdenum bisulphide additive (as recommended for Guzzi bevel drives until recent models). All I can say is that it has worked very well in Guzzi gearboxes and bevel drives and has helped to reduce noise on older gearboxes. I have no idea as to its suitability on the M3W bevel drive and I note that there is also this http://www.motul.com/it/en/products/108 oil which is a modern synthetic gear oil that also claims to reduce noise.
I would suggest you wait and see how your car is before you start to worry. You may have a fairly quiet bevel box