If I had to put all my money in 1 crypto, it will be Ethereum. I believe in Ethereum. Ethereum is popular due to rise in decentralised apps and smart contracts. Smart contracts may have many uses in future. Solidity is becoming popular among coding community. Solidity is the language used for programming smart contracts. Dapps are usually made on Ethereum blockchain. Building dapps on Ethereum is easy and fast. Ethereum allows anyone to write smart contracts and decentralized applications where they can create their own arbitrary rules for ownership and transition functions. I think Ethereum has many uses and thus I think its value may increase in the future. So if I need to choose only one coin, then definitely Ethereum will be my choice.