Mr Byrnes is contrasting fast to slow takeoff, keeping the singularity date constant. Mr Zoellner is keeping the past constant, and contrasting fast takeoff (singularity soon) with slow takeoff (singularity later).
Mr Byrnes is contrasting fast to slow takeoff, keeping the singularity date constant. Mr Zoellner is keeping the past constant, and contrasting fast takeoff (singularity soon) with slow takeoff (singularity later).