The difference is how the reference point is considered: for kinematic the reference point is master and the rest of the coupling points are slaves, so the slave nodes follow the movement of the master node. The distributing coupling has the reference point slave and the rest of the points are master and the force is weighted by the distance of each branch length.
Typical usage of the term master-slave is in contact.
I don't know how NASTRAN implements the constraints but in ABAQUS the motion of coupling nodes (in an element or node-based surface) is governed by the reference node in both kinematic and distributing coupling constraint. Element-based surfaces are usually the way to go, particularly in distributing coupling constraints.
Think of kinematic coupling as a "hard" constraint of rigid body motion on the coupling nodes. However, distributing coupling allows transmission of loads since the constraint is enforced only in an average sense ("soft" constraint). Depending on the coupling method employed, distributing coupling constraint has two sub-types: continuum and structural. No moments are transferred in continuum coupling, whereas in structural coupling both forces and moments are transferred (similar to what DCOUP2D and DCOUP3D elements allow).
However, distributing coupling [constraint] also allows transmission of loads since the constraint is enforced only in an average sense ("soft" constraint).
