(B)-Benzyl chloride would undergo faster S_N1 than (A)-Chloromethyl cyclohexane as the carbocation formed from benzyl chloride is resonance stabilized. In the case of chloromethyl cyclohexane the carbocation formed is primary. Primary carbocations are not favored by S_N1 reactions as a result it will not undergo S_N1 reaction as fast as the benzyl chloride.