One-year fixed interest rate is definitely lower than capital preservation fund, but the risk is almost zero.
Besides, I don't know which capital preservation fund you are talking about. As far as I know, there is no one-year capital preservation fund on sale at present. Capital preservation funds hold capital preservation at maturity, not always. If the fund lasts for five years, it will be guaranteed after five years. If you redeem it halfway, you may still lose money. I suggest you read the fund contract carefully. There is a big difference.