I think both are good and a diverse investment is a good idea. BTC is obviously valued a lot higher right now compared to ETH, but it's impossible to tell how their values will compare in the future. I do however fear that the value of ETH could decline after ICOs have run their course.
I prefer Bitcoin because Ethereum is like a copy coin and the Altcoins that are using it know that they are trying to milk the success of Ethereum till Bitcoin takes over again.