Don't listen to them, trade with what you like and make you profit more easily. Because for me it makes no difference trading in BTC or USD, so please adjust to your own needs. If you want to multiply your BTC then please trade with BTC, but if you want to make more your dollars then please trade in USD. Determine goal from now on and then trade without having to be confused anymore.
Generally i trade with BTC but sometimes i also fall into the trap like this. I think BTC trade is best in bull market and bear for USD. I don't know but somehow i think USD is the best option because USD market price don't drop hugely. But in many times you can see, you sold some coin with BTC, you collect it for buy some new coin after finish your research but next day you see BTC dump. You loss some bucks. It's happen to me and it's too much frustrated.
So if you prioritize fixed profits, please use USD in trading. But if you want to hold bitcoin while trading then use BTC as your trade. So my advice, it's better to trade in USD if you are a daily trader, crypto market fluctuations are so high unless you accept all the risks.