Both of these offer different advantages:
Bitcoin is the safest cryptocurrency and has reached the widest audience.
Not to mention holding a third of the entire market's value.
Ethereum is right there with it, holding second place on the ranks.
DApps, DAOs, and Smart Contracts changed the game.
So where do you bet your chips?
BTC or ETH?
In the best case, you have to have bitcoin and Ethereum in your cryptoperthite. But if you choose between them, I'll choose bitcoin.