These are stablecoins we're talking about, correct? These de-fi services have got to be doing something similar to what banks do, else there's no return to be had. If I owned any stablecoins (which I don't), I'd be way too afraid to invest them that way. Eek.
"De-Fi" protocols usually reward lenders with every stablecoin deposit. Rates can vary depending on how many people are borrowing coins on the platform. The lower the number of people borrowing, the lower your annual income (APY) will be. It's all driven by algorithms. The only risk would be losing all of your hard earned money if the stablecoin loses dollar parity in the long run. Of course, you can also lose it all with a PoS coin if it loses value. But at least you're not given false promises that they will always retain their value unlike stablecoins.
I think the only advantage would be sending "Fiat" faster and cheaper across borders. Not to mention, stablecoin issuers are able to "freeze" or blacklist your address from being able to send/receive any coins at all (you can do a quick Google search to see for yourself how USDC has been able to blacklist addresses in the past). It's the perfect tool for bankers to get what they want. Therefore, cash is the only solution if you want to "stick" with plain-old Fiat. Otherwise, I'd suggest you go all-in Bitcoin for the long term.