Both are the great investment. Although I think Etherum will have much bigger returns than investment in Bitcoin, Bitcoin is much safer. Bitcoin is the oldest and by far the most known and influential cryptocurrency out there. Ethereum might be a better investment for the simple fact that is has a much smaller market cap and better technology. If you are looking for the more consistent, safer cryptocurrency, bitcoin is the better investment. However, Bitcoin is better investment much bigger the most people though and it did the very fast.