There are thousands of crypto currencies. Many are clones of Bitcoin. While Bitcoin is specifically designed to transfer money, there are complex systems that also use the blockchain technology, but are mainly designed for secure and decentralized application of programs (contracts), and apply the transfer of money only as a minor matter. Ethereum comes first in this category.
Andreas Antonopoulos has bitcoin and ether compared to lion and shark (or vice versa). Another comparison would be that of a spoon with a pocket knife with 100 functions. While Bitcoin is designed to exchange values, Ethereum is a system for creating, managing and executing programs. Compared to Bitcoin, which has worked without errors up to now, Ethereum is highly complex and will continue to be improved. Since users program functions, a huge number of contracts and functions are conceivable. It is to be assumed that especially in an initial period, errors will happen. Pure transfer of funds is therefore a matter for Bitcoin and not for Ethereum.
In addition to a number of ether clones, there are independent crypto currencies, some without blockchain technology such as IOTA.
Some crypto currencies may use blockchain technology, but they discriminate against common users/owners. For example, the Ripple (XRP) allows only a few members of the consortium, mainly banks, to manage the database (Ripple has no blockchain).
Of course, the question of which crypto currency is the best investment cannot be answered. Since Bitcoin is the oldest currency, an investment in Bitcoin is less risky than in young and more complex crypto currencies.