Stylistic considerations too, such as the use of vibrato are ultimately his responsibility. Flexibility and the ability to play in all styles is paramount. The other players in the saxophone section must learn to blend with the leader and listen carefully to him at all times. To do so will ruin the overall cohesive sound of the section. A quick glance at the score or parts will tell him that a definite stylistic approach is needed.
Lets go through the score from the saxophones perspective.
This requires very careful listening. 5 saxophones must sound as one. Perfectly in tune with spot on phrasing. Nothing shows up the faults of a section more than unison playing, with maybe the exception of long notes played at a slow tempo. Let's break down the requirements for good unison playing.