I dont think that we should be worried for USDT, that is safe and for sure most of the investors are using USDT
Safe or not, depends on what aspect do you consider. If you consider its audit transparency, I can say it is quite risky and not really safe. But if we consider how many people use USDT, it is surely safe enough with its high market caps and strong support from crypto community.
USDT is the best when you want a stable coin
I am not sure to call it the best. I never compare it to other stable coins, but considering the issue related to USDT, I think it is not as the best as you think. Other stable coins probably have better performance and with no negative issues.
USDT has also a lower transaction fee compared to other stable coon.
What network?
For TRC20, yes it is cheap transaction fees. But for another network, the transaction fees are quite expensive.