Choosing over two promising coins to hold is just so hard to do, because they have different characteristics that will make you like them both. Bitcoin's price is really high which is simply amazing. While Ethereum's value is getting stable right now that may be a great factor for the future.
         It's really hard because my mind is full of "what ifs?". For example, what if you hold Bitcoin now then suddenly it reaches its price's peak and drops it's price in an instant? What if you hold Ethereum for long but it didn't progress at all? Such questions may change everything so be careful in choosing the coin that will suit your need. But now i'm on the BTC side.