Both are the best, none is better than the other because both offers same thing, stability against crypto volatility, and also both are controlled by centralized entities.
BUSD is from Binance and Binance is known as a good exchange, thus they will make sure they protect their coin against all odds, also BUSD is gradually getting supported by a lot of exchanges and thus having a good trading volume and market cap. USDT on the other hand, is also supported by all exchanges as well as different blockchain networks, but in all, it still offers same thing with BUSD.
The only difference I can spot out between USDT and BUSD is, USDT have a bigger market cap and support by different blockchain networks than BUSD, but with time, BUSD will still catch up with it. Moreover, most exchanges are now developing their own stablecoins and therefore this will keep reducing the attention on USDT, hence since all will offer same thing, I can't say any is better than others.