Both stablecoins really serve the same purpose, but they differ a lot in the way they operate with respect to the network they are built on, automation, complexity etc.

UST has the advantage of being the oldest, while DAI has an advantage of open-source, trusted and decentralized.

UST has counterparty and credit risk, but DAI has an issue with its complex design.

With this in mind, one needs to decide what suits their needs the best.

UST is great for traders, as it can be used in a more comprehensive way on exchanges for trading, but if one is looking to shop on DApps, DAI is helpful.