the best coin for holding 2021 is the coin that has the most demand, is Ethereum,
if the dominance of Bitcoin breaks down, investors will switch to Ethereum,
this has also happened during the altcoin season.
I don't think Ethereum would be a good coin to invest in this time around. Do you think there were a lot of whales buying ETH from as low as $ 100 - $ 150? And when Ethereum 2.0 comes along, that's when they sell off and kill greedy little fish. So be careful and never all in any investment, anything can happen in the crypto market.
For me i think ethereum is still the best altcoin to invest in so far. I can see the price of eth will continue to rise up like bitcoin. I can imagine ethereum price by the end of the year is around 700$.