Green: Attach point to chassis
Purple: Detacher Arms Yellow: External Traveling Arms
Cyan: Load (usually a wheel)
Lime green:Internal traveling arm.

From left to right pros and cons,

Detacher only:
Pros: Simple, soft, bouncy, has largest freedom of travel,
Cons: bouncy, soft, uncontrollable travel direction.

Detacher and double rotor:
Pros: Allows the load to rotate along the travel arms axis, Not as bouncy as Detacher only,
Cons: allows the load to rotate around the travel arm axis, heavier, more parts

Detacher and single rotor:
Pros: Stiffer, keep the travel of the load to just one plane, almost no bounce
Cons:Only allows the load to travel up or down side loads can damage the suspension.

The longer the Yellow arms are (thus the farther the cyan load is from the green attachment point) the softer the suspension, and the more travel space required.

The more purple detachers you have the softer the suspension will be, (this is the easiest way to soften a suspension) as well as the bouncier it can become.