Double Uppercut: not so interesting?

But what makes DU -> FF x2 -> repeat (I'll call this A) that much better than FF x4 -> repeat (I'll call this B)?

A is 1.98 seconds long and totals 1120% damage
B is 2.04 seconds long and totals 1080% damage

What's so amazing about such minute differences?

It's obvious.
40% more damage and a few seconds of stun.