Considering the volatility of Bitcoin, I'd preferred to this compared to altcoins. But because we can't just rely upon a single trade, having altcoins is also preferable. Most of the time I use to choose coins that are quite active and moving in a zigzag direction as I can easily make a buy/sell option which makes me not feel bored waiting to get fill/refill.
Of course, using stables coins like USDT as for trading pair is a great idea.