Etherium is a better coin since it also has the smart contract feature. There is nothing that you can do with bitcoin but you cant with etherium. So why not all people sell their bitcoin and buy etherium.
If you base your argument on smart contract feature alone and are already a fan of Ethereum then probably the coin will always be heavier than bitcoin for you. But I am basing on the entire existence of the two coins, their features and acceptability, and bitcoin is number one for me.