What is a Jolly Choice Scarf Flygon significantly outspeeding, that an Adamant one isn't?
"A Jolly nature can also be used to revenge kill a neutral Speed nature Dragon Danced Salamence, but the power drop makes it a poor option."
http://www.smogon.com/dp/pokemon/flygon
I'd say Jolly would be good for outspeeding other neutral speed nature scarfers as well as Dragon Dancers. Other than that, idk.