Which would undergo SN1 reactions faster in the following pair?

In the SN1 reaction, the big barrier is carbocation stability. Since the first step of the SN1 reaction is the loss of a leaving group to give a carbocation, the rate of the reaction will be proportional to the stability of the carbocation. Carbocation stability increases with increasing substitution of the carbon (tertiary > secondary > primary) as well as with resonance. CH3CH(Br)CH3 is faster than CH3CH2CH2Br.