Answer is: fewer drops of 6 M sulfuric acid, because concentration of H⁺ is greater than in hydrochloric acid with same concentration.
Chemical dissociation of hydrochloric acid in water:
HCl(aq) → H⁺(aq) + Cl⁻(aq).
Chemical dissociation of sulfuric acid in water:
H₂SO₄(aq) → 2H⁺(aq) + SO₄²⁻(aq).
From chemical reaction: c(HCl) = c(H⁺) = 6 M.
c(H⁺) = 2c(H₂SO₄) = 2 · 6 M = 12 M; concentration of hydrogen cations.
