SN1 rxn involves the formation of carbocation........so ...more stable the carbocation more is the ease of formation of it and faster is the rate of rxn.........polar solvents like water stabilize the intermediate carbocation by coordinating with the +ve end of the carbocation and hence the ionisation will be faster .......... so polar solvents are to be used for an SN1rxn....so now u can know who is correct....