Network is the main factor here to determine it. We all know that eth network is higher in comparison with BNB. If you would like to spend less gas fee, you should go for using BNB based network. Because of expensive fee in Eth network.
USDT is also on the BNB network as well as on many other networks, only if to save costs and want to swap to stablecoins then a very wise choice would be BUSD, but that is not in the choice of topic, which is a shame.