Both USDT and BUSD is so good. But I think overall USDT is good and more popular and uses by every trader. You can exchange your coin to USDT in most of the exchanger. But you can't convert your coin to BUSD in only Binance platform. Also USDT withdraw fee is low and transaction fee is low. So this is more preferable.
For that reason, I think most Binance users prefer Binance USD while other traders who don't use Binance would more prefer Tether USD. I don't think any of them is better than the other because both the coins serve the same purpose and only trust might be the difference and for that part, I trust Binance more than Tether.
Traders prefer using USDT over BUSD but the truth there is That the two coins are both stable coins and are very good, USDT is more popular and is listed in many exchanges than BUSD and also USDT is more preferable because of its popularity, traders find USDT pairs more convenient in trading than any other stable coins.
Tether has a bigger volume too and hence a more packed market. Traders are used to of trading in USDT and hence they don't want to change it unless they face some problems.
I do use USDT sometimes because not everywhere BUSD is accepted, but nowadays I have moved to TRC-20 chain because of the high transaction fees on the ERC-20 chain.