There is a huge difference between Tan Cheng Bock and the PAP Malay candidates.
Tan Cheng Bock had resigned from PAP for many years now and has been treated like an outcast by PAP, he is largely seen as independent and non-partisan by the people. The Malay candidates are current PAP members and are extremely beholden to PAP for their very overpaid public jobs and minister pensions.
Tan Cheng Bock will be an independent president not beholden to PAP and not afraid to speak out, while the PAP Malay candidates will be like quiet obedient PAP puppets/dogs doing whatever their PAP master tells them to do.