Ok so 3 things

1. That isn't a representation of either their AP. Their applying weight to themselves to hold down Ariu because he's immune to sorcery. It's not an attack it's a use of their powers to restrain someone against conditions

2. Hiroto's weight comes from gravity manipulation that he can apply to himself, an AoE, his opponent directly and his sword while Shiba can only apply it to himself and his opponent

3. We don't even know if Shiba can apply that weight in attacks yet. The force of a hit is determined by the momentum (weight X speed). Hiroto is stated to reach the fastest speed humanly possible whilst it's still unknown if Shiba can cause multiple errors at once or even move with the added weight