To SRS or not to SRS? Would I be better off paying the upfront taxes and simply investing cash and enjoying the tax-free dividends and capital gains?

Depends on your tax bracket... the higher your tax bracket, the more likely that the tax savings are "worth it".

Assuming you top up SRS $1,275 per month for 40 years, that's $612,000 net deposits. Assuming CPF SA interest, the final value will be around $1,400,000.

Then you withdraw $140,000 each year. $70,000 minus some personal reliefs get taxed.