this is my advice:
for young pple (or new couples), do not transfer OA to SA becos u can use OA to buy house and for other purposes. the trsf is irrevocable and the money will be locked down until u retire.
if u have already bought your house, or no need to use OA for any purposes, it is a good idea to trsf OA to SA as the interest rates is higher.
also, if i am not wrong, i think there is a cap as to how much u can trsf to SA. u can check the CPF website for the cap b4 trsf.