Which is better to DCA $200 into S&P 500 ETF every month, FSMOne or Kristal AI?

You can sign up for FSMOne RSP, which lets you invest in VOO & IVV from $50 a month.

From that perspective, FSMOne may be a better choice.

If you're looking for S&P 500 ETF exposure, Syfe Equity100 is pretty good too. It holds CSPX which is LSE listed so your withholding tax on dividends is 15% instead of 30%.

Just wanted to check ... I see that VOO is currently trading at 352 USD, so $200 SGD won't be sufficent to buy even 1 unit of VOO. Perhaps you might want to consider using robo-advisors, like Syfe's equity 100