Well, it's meant to be even. But, I'm guessing you want an answer...
I mean, the gravity sword has a moderate range. And, if you are not quite close enough to kill someone, it only half-damages them.
The sword is okay. If your close enough you will lounge toward the opponent, maybe killing them. Yet, if your opponent has a sword too, and you both attack at the same time. You both get damaged, but nether one of you dies.
If I had to chose, it would be the sword, sense they are about even. But the sword looks freaking sweat!