both are good investments in 2018.I think both have potential. consider both Bitcoin and Ethereum as both were alredy known  by many people and the demands by people is higher than other coins.

I will go for Bitcoin. Bitcoin will still rule the cryptocurrency. No coins can overtake the price of bitcoin as the year ends. It will go higher and lower as time, but I beleive it will still maintain its lead. Bitcoin is the first and the original coins we have, very expensive and valuable one. So, I will still choose Bitcoin.

Bitcoin for sure, without an iota of doubt. Tell me what is ethereum actually used for today except to fund ICO's. The answer is nothing, absolutely nothing at all.

Being the number one cryptocurrency in the market needs a satisfying value. Bitcoin is still on the top of having the highest value even it dropped from 20000 back to 8000 or less. Ethereum boosts its value but it also drops its value. We all can't say what will happen next, if it will be the boom or the bust period. On this year I am hiping that most of cryptocurrencies recover their price and if that happens, I think BTC will rule in 2018.

The main coin is always bitcoin. But for 2018 I would advise to create a portfolio of several coins: bitcoin, etherium, dash and a few other coins that you like.

As it seems to me, both options are good enough, they are both popular and have a huge potential to be leading for a long time in the world of crypto currency

Bitcoin will still rule in term of marketcap. For price wise, both BTC and ETH will have good gain. Hence I will choose to invest in both coins.

Both will survive, I use both because it is the strongest coin. Bitcoin and ethereum will increase in 2018.

ETH by the end of 2017 showed who the owner of the market 

I don't think there needs to be only of these ruling. All of them have potential to rise a lot. I prefer Eth after what has happened with btc txs fees, but bitcoin will always be there as a flagship of the whole industry. Don't forget about ltc though