To answer this question you need some more information and a forecast model:
1. How long will the transfer dollars be held in SA (versus OA)?
2. What's the marginal tax bracket (and thus the tax relief amount)? How will your marginal tax bracket change? (Will you be in a higher tax bracket in the future?)
3. What are the dollars saved on income tax going to be doing? Parked in a 0.05% interest bank account, for example?
4. What are the alternative tax relief opportunities, if any, and how will they behave? (Notable examples: Supplementary Retirement Scheme, CPF MediSave Voluntary Contributions.)
5. Is there some other family member in the picture, perhaps with tax relief opportunities?
6. Do you care about being able to withdraw funds to drop your future CPF Retirement Account below the Full Retirement Sum? (SA top ups, plus accrued interest on those top ups, are not available for lump sum withdrawal and must stream out via CPF LIFE.)
7. Do you expect to "shield" Special Account dollars just before your RA is created on your 55th birthday? How do you value this shielding? (SA top ups can sometimes reduce the amount you're able to shield.)
8. (Exceptional case: ) Are you subject to some other tax jurisdiction, and will any income tax relief in Singapore be "clawed back" by that other tax authority?
9. How much do you value housing-related liquidity and the CPF Investment Scheme (OA)?
10. How much do you value the asset protection attributes of CPF against creditors and court judgments (via cash top ups into SA)?
11. Are you, or will you be, self-employed and thus able to make "all three account" CPF Voluntary Contributions with tax relief?
12. How will your compulsory contributions behave over time?
"It's complicated!"
