What motivates a sailor more -- trying to catch the leader or trying to outrun a storm? I picture this kind of like a skier trying to outrun an avalanche. A little extra adrenalin there.
Definitely a storm. Senses are extremely heightened and you are pushing as hard as possible without flipping. Every thunderboom is another jolt of adrenaline. It's not like you weren't already sailing as fast as you could, but there's a new urgency to your sailing.
