They are both good as an investment, but I personally prefer ETH more than BTC. ETH has more use, including that you always can trade using it or participate in ICOs with it. ETH markets are on all exchanges along with BTC and USDT pairs.
But despite that, BTC is "our king" and probably it is worth considering to buy both of them for hold. And taking into account current market condition, when I say "for hold", the "hold" will be rather long term than short term