G'Day Mick,
I have a pretty limited experience with monopods, so don't take what I say as gospel.
I have a trekking pole with a 4/20 thread in the top under the knob so it doubles as a monopod when bushwalking.
For long exposures, existing light and shady scenes, the tripod will definitely be better. If your lens is IS you might get away with a bit more on the monopod. Both will take the weight off holding the camera in long sessions, but the monopod is quicker and easier to move about. Both should work OK for panoramas with todays software.
Al.