Just want to share my understanding of the rss and cpf life.
To me, CPF is a supplement to retirement fund.
RSS allow us to totally cash out from CPF minus the medisave

which is tied up based on ground that when we need medical assistance, we can use the fund. Funds in RSS continue to attract interest while it is getting drawn down.
CPF Life has 3 plans which will payout for as long as you live. 2 of plans which does not attract interest (1st and 3rd plan, if I remember correctly) while money is tied up in the account as it goes to a pool. We continue to draw down our money till it's fully withdrawn and then it starts to draw from the pool till we pass on. Similarly to RSS, medisave is lock up and use for medical needs.
My top choice is to fully draw out CPF at 55, follow by RSS and CPF Life.