I think one of the reasons why Bitcoin trading is the best and the best is that when one trades only Bitcoin, his profit will be less than other coins or tokens and vice versa the chances of losing from other coins or tokens will be much less. I personally think that Bitcoin can be the only product for long-term trade management or long-term planning.
If this is for long-term trade, or meaning long-term investment, I do agree that Bitcoin is the best crypto for long-term investment. The proof has been clear, it's trusted. But if this is for daily trades, I think that many traders will also love trading altcoins that have high market caps, or moreover, the new hype with high risks, because they can also earn money from it. But as I said, this will be exactly risky. However, altcoins with small prices will help us to gain more profits than trading Bitcoin moreover if our amount of capital is still small. However, once more, this will again depend on how our trading strategy and habits.