My suggestion is, don't listen to what others say, but make a trip to CPF office and speak to an officer there. Prepare a list of questions that you want answers.
You will be surprised at what you hear! I had a choice (I am older and not compulsory) so I decided not to sign for any of the scheme. You can draw your own conclusion from my decision.
If you must choose, speak to CPF before making a choice.
Thank for your advise.