BNB and USDT are two different things. Usdt is a stable coin. Bnb is constantly increasing and decreasing. In my opinion it is better to keep usdt according to the current market if it is a small trader. However, BNB still has a long way to go.
For holds, BNB as a good choice if you believe it will be more than its last ATH.
On USDT, if you want to do transaction on it most of the time just avoid the protocol on ERC20. The fee ain't cheap and that's why you should choose the tron network or any other protocol of it that has way cheaper to send.