With the speed of USDT minting from Tether company and with the huge supply of Tether USD on the market, the risk for USDT and the company are higher than Ripple. There are many accusations, lawsuits on Tether in the past and will have more in the future. The more improvements on law regulations aim at crypto market, the more risks of shutdown, seize, drama Tether will have.

It is a very old story that warns us the fact behind stable coins: They can be frozen by governments.
[UPDATED] PSA: Most Stablecoins Can Be Frozen, Even in Your Own Wallets