Why should I use deformation bones instead of just parenting w/ automatic weights straight to the armature? The octahedrals act as bones while adding keyframes... However would deformation bones possibly lessen the possibility of import export errors especially to UE4?
When you generate the rigify rig after adjusting the initial meta-rig and pressing generate in the armature tab (in the properties window), rigify genetates a host of control bones with ready made complex behaviors such as IK, foot roll, fist open/close, and many more.
If you're animating the deform bones directly, and ignoring all these features, you probably don't need to generate and can bind to the meta-rig directly.