SWMM solver and Implicit Solver

Hello everyone,

In SWMM Reference Manual Vol 2-Hydraulics, page 45: They said that SWMM 5 use an implicit method.

- Please tell me why Bentley called it "Explicit solver" in SewerGEMS.
- Is there a document detailed on different between Implicit solver and Explicit solver?
- I have read the Bentley's Guide : "The implicit solver tends to be more stable with pumping situations. The explicit solver tends to be more stable with fast changing areas such as ponds or control structures"
But if my model has both elements (pumping station and pond, control structures, etc.), what should I rely on to choose the right solver?