Thanks everyone for their reply. As the shielding will be done in the first week of Jan, T-bill does look like the best option right now. No one knows what the future holds so we could only make decision based on what we know.
The next T-bill (if used for SA shielding) will remove funds from the member's Special Account during months spanning 1Q, 2Q,
and 3Q of 2023. We only know the SA interest rate (4.0%) for 1Q2023.
Unit trust-based shielding ordinarily loses 1 month of SA interest, and if that's in 1Q2023 (January, February, or March) you already know that will be only 4.0% interest (annualized). You don't know exactly what the unit trust will do while you're holding it — it may go up a little, it may go down a little — but you're only holding it for days or maybe 2 weeks at the most. With the 6 month T-bill you don't know exactly what its rate will be (that depends on your bid and the auction) until you get it, and you don't know what the outer months of lost SA interest will be (except at least 4.0% annualized) since 6 months is always beyond the CPF Board's rate announcements.
If the T-bill rate is high enough then this SA rate risk can be overcome. Give some thought to how high a T-bill rate you need to overcome the SA rate risk. And then, if your bid isn't filled, you'll have the unit trust-based method as a fallback.
