Flashing blade or fury

So I'm building up a +spd -def Shanna and I'm wondering what would be best for her A skill
Flashing blade would pretty much make Iceberg a 1 cooldown special which is really good, and it also scores high in the arena
But fury 3, even though it scores less, boosts all stats and of course you lose 6 HP everytime you fight against a unit, but it synergizes with Desperation