If you have 10000$. It's better to buy ethereum. 2018 is the year of ethereum

Buying bitcoin next year wont give you alot of profit. It might increase in value but not twice its base.
Best of luck
How sure are you that next year is the year for ethereum? No one can tell if what will happen on the prices of the crypto currency. It will really depend on the demand that the coin will have. Bitcoin's price will continue to rise on the next years and I don't think that Ethereum will be able to go over it's rate in the next years.