I would definitely but both because diversification is actually a good thing in Long term. I will divide my investment by 33% to Bitcoin, 33% to ethereum and the remaining 33% to different altcoins and ICO's.
Do you think ethereum is growing up in some years and you invest 33% in ethereum I know you are destroy you all money of invest in ethereum I give you a little suggestion your 33% invest in ethereum you invest in bitcoin this is better for you in your future.