Assertion (A): Anilinium chloride is more acidic than ammonium chloride.

Reason (R): Anilinium ion is resonance stabilised.

Anilinium chloride is more acidic than ammonium chloride because anilinium chloride can form salt with water and liberate amine when treated with a strong base.

$\mathrm{Ph}-{\mathrm{NH}}_3{{}^{+}\mathrm{Cl}}^{-}+\mathrm{NaOH}\to \mathrm{Ph}-{\mathrm{NH}}_2+{\mathrm{H}}_2\mathrm{O}+\mathrm{NaCl}$

Also, resonance in anilinium ions is not possible because charge dispersion at the ring may involve pentavalent nitrogen structure which is very unstable.

Thus, the assertion is true but the reason is false.

Hence, option (C) is correct.