Very different projects indeed. I believe bitcoin will gain market share and develop as a reserve cryptocurrency. Institutional money will first some to a more established, time tested crypto, namely bitcoin. This will lead to gain in market dominance for bitcoin.

Once regulations on ICOs are clear and in case a better ethereum alternative is not found/ethereum developers find a way to make ether scalable, then we will see more money going into ethereum. I am more bullish on btc than eth for 2018.