When ETH is still at around $300 I switched to BTC since it was unstoppable last year however this year ETH pumped and I regret that decision because of that I decided to hold both of them 60% ETH and 40% BTC. I am holding both of them but when I see another altcoin to invest with I'll use my BTC and will hold the other. Honestly, it is very hard to decide which coin to hold since I don't have a lot of idea in trading/investment but one thing that I am sure of, ETH is the future and next BTC in the making.