For me USDT is most preferable. Here has some reason :
Though there is no matter of cex or dex because both of are centralized. But busd could be has documentation from binance for sec reason. Where usdt could be in problem.

But usdt has the biggest option which is we can use usdt in any kind of nework like ethereum , tron, omni, binance, tomo, thubder means every blockchain network support usdt. That means it is quite easy for us to grab any kind of Blockchain project if we have usdt. But here has the problem of busd. Because it is Only support binance based project. And also it is in only binance. Not other exchange support busd. So now i hope you understand that usdt could be easy to use than busd.