Speed versus geometry. That is most of the decision, and it gets made at the survey rather than at the gate.
When system scaffold wins
Repeatable elevations, a clear footprint and a tight erection window. Ringlock and cuplock go up fast because the components only fit one way, which also makes them easier to inspect and harder to get wrong.
When tube and clamp earns its keep
The moment the building stops being rectangular. Curved facades, plant rooms, stairwells, protected stonework you cannot drill into. Every joint is made on site, so the scaffold follows the structure. It costs more hours and saves the whole job.
