I recommend to stop on bitcoin, as experience shows, this currency is more stable than the etherium. Recently, the etherium surrenders its positions, many fear that this currency will become completely irrelevant. Forecasts are not very favorable. Keep better means in bitcoin - for some time this coin to last the first and stable. But you need to understand this is a long-term investment, in order to make a profit it will be necessary to wait for the market to recover.
Well, to be honest I think that Ethereum has more chances to double the price than bitcoin but these both get increased together with a small difference, sometimes bitcoin goes higher than ethereum in % change.
If I were you I would split the balance half in ethereum and half in bitcoin, if they both go higher at the same level then you are safe, but if one goes higher than the other then you are in profit.