Minecraft wiki entry for Slow_Falling, associated text: Sprinting with the Slow Falling effect allows the player to jump across a gap of 5 blocks (6 blocks with enough momentum), compared to 4 (5 blocks with enough momentum) blocks normally.
Unboosted elytra flight is twice as efficient, but four times slower. Boosts work at normal speed, but the momentum gained doesn't last as long.
The player cannot land a critical hit while having this effect.