its very difficult question to answer. both of them are good currencies with high future potential. bitcoin is the king.etherium is queen. but etherium is very much cheeper when comparing with bitcoin. so i recomend you to buy etherium rather than buying bitcoin. it will have future high price movements. some predicts it will mark usd 5000 at end of this year. majority of new projeccts based on etherium.they are erc20 tokens wich based on etherium network.other thing is transaction fee. with comparing with bitcoins etherium has very cheep transaction fee. also transaction time is very less compaierd to bitcoin. those are the major benifits of investing on etherium other than bitcoin.so i strongly recomend you to invest on etherim rather than bitcoin.goodluck