I will choose ETH, we all know that both of the coin is volatile and they don't have stable prices, eth have more potential to increase because of its low capitalization, they have proven it last year and its more than 2x of its price today, while bitcoin has potential but in a long term investment.
I would also choose ETH. I also think that the price for ETH will grow faster than on the BTC. And by the end of the year the profit will be greater.