Bitcoin is the original and some liken it to digital gold. It recently forked as there were competing camps who couldn’t agree on how to scale for increased capacity. This disagreement has in my option cost Bitcoin it’s completely dominant position - 2 years ago, Bitcoin was >90% of the crypto market, it is now about 55%.
Litecoin has no real benefits over Bitcoin - pretty much the same technology.
Ethereum is not really a coin as such, but a general purpose computing system fuelled by ether. It has two major problems in my view, the first being that it is really hard to write safe smart contracts in a general purpose language and this has resulted in hackers being able to steal millions of dollars worth of ether. Ethereum hard forked last year because of one such hack. If even the creators of Ethereum can’t write solid smart contracts then who can? The second problem is that Ethereum production is unlimited, they can just keep making more. I consider it to be a huge scam coin.
In my opinion, the most interesting coin is Monero - it actually does what most people think Bitcoin does but doesn’t. Bitcoin is NOT anonymous, every transaction is saved for ever to the blockchain. If I know your public Bitcoin address, I know how much money you have, where it came from and what you like to spend it on. Coins are not fungible as they can be and are traced by blockchain analysis systems. If you are unlucky enough to purchase Bitcoin that has been used on a dark market or associated with terrorism, you may find it unsellable in the future. Monero addresses the privacy and fungibility issues that Bitcoin has by using a new algorithm that mixes multiple public keys into each transaction, making it impossible to track who is spending, what a wallet contains or where the money is going. It truly is digital cash, better even as cash still has serial numbers.
Its value has increased by over 2000% in the last year but is still a fraction of the Bitcoin market cap, at just over $700 million, because it is still in its infancy. It is not as easy to use as Bitcoin yet, but it has a very active development team and its inherent advantages will eventually win out in my view. The other thing that impressed me was that it wasn’t pre-mined before release.
Many coins have all of the easy early coins mined before anyone else gets to hear about them - Satoshi has millions of dollars of Bitcoin as he mined thousands of coins before releasing the software.