I suggest BNB because bnb is raising price day by day . And the usdt is stable crypto currency. If you just want to save your portfolio then you should select usdt but if you want to earn and want to get some profit then you should select bnb.
BNB only goes up when the market is in good condition and when Bitcoin starts to move upwards, if those two things are not present, then BNB can also experience a price decline as it is now, so it's not always an increase in BNB's price, this is what you need to understand too.
of course, the progress of the BNB market can also be affected by the bitcoin market. and it is very easy to fall if the market conditions move in a negative direction like today. most altcoins can't fight the market dominance created by bitcoin. and it will always bring the movement for altcoins.
but it will be different for a stable asset like USDT. when the market is in a downtrend, then we can see the adoption of stable assets will increase and that will increase the price. although not in high value.