Which trading pair you want to choose. Suppose you want to trade a common coins which is listed in both pair. Then which pair you will choose?
If i compare in binance BTC/ETH and USDT/ETH markets, Then i can see volume is BTC market almost 241,924 ETH.
I trade btc/Usdt only when I try to avoid volatility, it's always easy to hold Usdt when the market is tumbling with loss, this way you can safeguard your fund.
When trading altcoins, I prefer to used btc pairs. When an altcoins surge by 200-300%, I don't convert them to Usdt, I directly swap them to Btc because as soon as bitcoin start making moves, altcoins and their dominance will begin to fall.
Once altcoins season begins, I make sure I book my profit in Btc.