One-lines "usually" are used to show information about the electrical distribution system. Riser diagrams are "usually" used to show information about fire alarms, PA systems, telecom systems, etc...
In commercial building, EE typical using riser diagrams are more physical than electrical oriented. Usually show the physical relation of the electrical components similar to block diagrams with location and interconnection from point to point.
On the other hand, one line diagram (OLD) is more electrical than physical oriented. In general, OLD shows equipment capacity, rating, transformer configuration (i.e. DY, etc), cable size, SC rating, cont current rating, type of protective devices, and simplify interconnection among other generic details.
