I prefer to trade mostly BTC-based pairs as well since my only goal's just to accumulate and more Bitcoin, so just trading through BTC pairs eliminates any fees I might have to pay to convert USDT or USDC or any other stablecoin back into Bitcoin. I still do trade with leverage on sites like Bitmex for pairs such as BTCUSD simply because I've got good experience with that specific pair and I know how things go with it, but typically I do still trade most altcoins against BTC.
Okay, I personally hate USDT with a vengeance, they are a company that stole billions of dollars from people and they didn't get caught or jailed or anything, they are not even sued as far as I know right now because they did their shady business very
carefully.
We are talking about BILLIONS here, in order to make that much money you have to make 1 million dollars per month for 83 years just to tell you how much that is, and that is just 1 billion, they had some change as well, so they got away with 100 years of 1 million dollars per month type of money. So, I would definitely use bitcoin to trade and don't go near USDT, however there are other more legit stablecoins people use and I may understand where they came from, its easier to live with fiat than bitcoin because world is still mainly fiat.
Between USD and BTC have benefit when trading but I think we earn much profit if trade with bitcoin, USD price look stable and never change with higher or lower price where we only get profit from our coin price only when trading, but using bitcoin as trading peer we can get double profit not only with coin have higher price but when bitcoin up we got double profit too.