Interesting, I am facing the same situation and asking myself the same questions. Here're my comments and even more questions.
1) I am slightly inclined towards retirement plan (with annuities) and I will probably do lump sum premiums rather than to keep paying till 60. Reason is if I get lump sum from wealthbuilder, I oso don't know what to do with it, might as well get annuities. Although, I might ask my FA to do a IRR calculation of the cashflows between wealthbuilder and retirement plan to make the final decision.
2) On top of deciding btw retirement plan and wealthbuilder, I am also trying to figure out the sweet spot between one of the above mentioned 2 plans and CPF life. Especially since CPF is sort of compulsory, it has to be evaluated along with other plans. CPF life - advantage is that I don't pay premium until I'm 65 so have cash vs opportunity cost. And meantime, can top up SA and lower tax. But when I am indeed 65 (27 yrs from now), the premiums for CPF FRS will higher than the current $161000, so must make sure the cash earns a better rate than what will eventually be the FRS $amount when I am 65. (but monthly payouts will also be adjusted upwards along with FRS adjustment - I think)
When I figure this out, then I can figure out how much "more" to put in retirement plan or wealthbulder.
Any advice or did I totally misunderstood some of the instruments/products?