At the airline I fly for it is the Captain's responsibility to reject the takeoff. The PM will call out the malfunction and, as the Captain always has his hands on the thrust levers, he will initiate the rejected T/O.
CRM is for who pays for the first beer. Just kidding, CRM has it's place but a rejected T/O is not one of them. CRM is useful for situations where there is time to set up a plan of action.