If you are young and aggressive, maximizing CPF balance is definitely not the way to go.
The available data do not agree. See downthread for the dollar cost averaged STI ETF total return comparison, but looking at 5 successive 10 year periods of dollar cost averaging total STI ETF returns have been averaging about 4.14% with taxed money, which is just not good enough to beat MA/SA/RA at 4.0% plus bonus interest and pre-tax/never taxed money. Moreover, CPF balances are creditor and judgment proof, worldwide. If you're "young and aggressive," that aspect is also quite important.
Also, if you nail down CPF you can prudently be that much more aggressive (and still young) with your other monies. As you de-risk one part of your total portfolio, you can prudently up-risk the rest, ceteris paribus. So you've got a weirdly better-than-STI ETF bond-like part of your portfolio...and can still punt 100% on stocks (and cryptocurrencies and dubious business ventures and South American rubber plantations...whatever) with your other money if you like. Wow, that's awesome, sign me up. (OK, except the cryptocurrencies and dubious business ventures and rubber plantations parts.)
On top of all that, there is something called the CPF Investment Scheme if you wish, if you're "young and aggressive," and you get to punt using pre-tax/never taxed money. You can also go pursue your dreams of real estate tycoonism with your OA funds, again with pre-tax money. (Although property investing itself is taxed.)
Work the system, that's all. Play the game well, and there is lots of game playing opportunity here. Not
infinite opportunity -- CPF is strictly capped -- but it's an excellent tool.
If you are older or low risk taker, maximizing CPF balance might be better.
Might be?!?!?
Who else is offering 55+ year olds (or near 55s) a AAA rated, Singapore dollar, on demand savings account at >>2.5% (blended OA and SA rate) with up to $37,740 in annual deposits?(*) That's one hell of a fixed income investment!
(*) Assumes FRS (or BRS with property pledge), and thus lifetime retirement income, and BHS attained (and thus medical financial security).