I will definitely go for ethereum cause have been observing the market cap and ethereum has been one of trusted altcoins so far. It's likely that ethereum will reach an ATH but since the market is unpredictable and the price of ethereum keeps fluctuating so I can't give reasons
The reason why I choosed ethereum, it's a good investment choice like bitcoin, although ethereum investment sounds risky due to the volatility nature but it's a kind of invest for long term so investors who are used to long term can still choose ethereum.