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.