Both have some of the highest liquidity in the market, making each a no-brainer for intraday trading. Also, both are susceptible to news- and tweet-induced price swings within the day, which can sometimes be quite drastic. If you prefer scalping, than you’d also want to keep the BTC charts at hand at all times, as most major altcoins mirror its price movements to some degree. BTC correlation is sometimes crucial to watch out for, especially in a bear market.
Also, at the time of this writing, Ethereum is fresh past its transition to Proof-of-Stake (aka the Merge), meaning a new surge in buying & selling power for ETH and even more liquidity that before. For many, day-trading the second-largest altcoin is now more profitable than ever.
However, there are some other notable coins that most often fit in the above criteria. These include:Dogecoin
is one of the top picks for most full-time day traders.