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.