Depends on you. I opted for private since it will definitely be a match for my baby and I chose Cordlife in the end, since they are the most established in Sg. I have friends who opted for public bank, but it means any one who match can use the cord blood.
Private and we paid one lump sum as it will be cheaper. If is public it is free if I am not wrong but the cord blood stem can be used by anyone who matches and needs it.