Of all coins, Bitcoin, Ethereum, Litecoin, and Bitcoin Cash are solid picks for a few simple reasons. 1. they all trade on Coinbase and Robinhood (both are established U.S. companies) and 2. They are almost certainly all not securities.
Bitcoin is the most stable in terms of price and the most popular, and then Ethereum. Meanwhile, Litecoin and Bitcoin Cash are less stable and offer a bit more risk/reward in terms of price.
The charts aren’t exactly the same, and they don’t all have the same transaction speeds or use cases.
Still, due mostly to what they do have in common, all four are likely to withstand the test of time moving forward (and all but Bitcoin Cash have withstood the test of time so far).
They might not be the coins that preform the best, but they are solid picks due to the liquidity and familiarity that Coinbase and Robinhood provide, due to them being some of the coins most often accepted by venders, and due to their standing with the SEC (where Bitcoin and Ethereum are not securities and logically that means Litecoin and Bitcoin Cash aren’t either due to Litecoin being a bit of a Bitcoin clone with no pre-sale and Bitcoin Cash being a fork of Bitcoin).
The logic is simple, but it is worth keeping in mind when figuring out which coins you want in your portfolio.
NOTE: The day after I wrote this Coinbase announced they are exploring adding Cardano (ADA), Basic Attention Token (BAT), Stellar Lumens (XLM), Zcash (ZEC), and 0x (ZRX) to Coinbase and Coinbase Pro for buy / sell / trade. Likewise, they had announced they are adding Ethereum Classic (ETC) for buy / sell / trade before. Since they are adding ETC, that should be a solid play for the reasons above. If they add the other coins, then those will all become solid plays for the reasons above as well. The idea being we are simply applying the same logic to any coin that trades on a major US exchange, that is beginner oriented, and provides a lot of USD liquidity to the market like Coinbase.