It seems a number of brands prefer SDM masts to be used in their sail particularly the bigger sails. Some brands enable the use of either RDM or SDM in their cammed sails. Some brands cammed sails below 6m used RDM only and above 6m SDM only.

Forget about strength and durability because I guess RDM would win that one. Which SDM or RDM will you get the best performance from a freerace/Race/speed sail? I guess it comes down to the aerodynamics around the wider diameter of the SDM over the RDM.