ETH has many advantages, such as faster transaction and lower transaction cost. Many projects are based on eth, and it will continue to develop in 2018. I think the market share of ETH occupation will increase this year, but from the perspective of investment, I still choose bitcoin. I can only say this is a kind of investment preference.
The thing is, that bitcoin has still an enormous reliability and popularity because it was the one that started the whole thing, ethereum on the other hand is a really polished project but needs way more time on the field to achieve greater things.