1. IOTA - 2000m marketcap - first mover advantage, great partnerships but extremely high valuated.
2. Bytecoin - 430m marketcap - i need more research on this, but highly valuated for my taste.
3. Rchain - 140m marketcap - great code, but still proof of stake, which is plutocracy, rich get richer scheme.
4. Holochain - 110m marketcap - good code, unique ideea of not having a consensus, nice contender to all in - decently valuated showing loads of x10-x20 potential if it matures and is successful.
5. Constellation - 8m marketcap - good code, similar to rchain, but a far better consensus based on meritocracy, how well nodes perform. The main selling point of this one over the others is the fact that the busier the network, the faster it gets theoretically. Upside potential is huge, it needs x14 just to reach Holochain's marketcap, its closest competitor.
Best coins I'd go for right now in this branch would be Holochain and Constellation. Seeing their upside potential, my final pick goes towards Constellation
Those are the best altcoins to buy right now. Most of them on the list are DAG-based cryptocurrencies which are proven to be much more scalable than PoW and PoS cryptocurrencies on the market. IOTA will be responsible of transforming the Internet of Things industry with its Tangle technology, while Constellation will transform the payments industry. When these coins take off, I'm sure that many early adopters would become rich as such coins become practical and useful in the mainstream world.
Bytecoin has a similar model to that of IOTA and Constellation, which could prove to become successful over the long term. Among the list of coins mentioned, I would like to add 2 more coins to the list and those are Ethereum and NANO. For obvious reasons, Ethereum should be on the top of your list of altcoins to buy, simply because it will upgrade to PoS in the future, becoming much scalable and secure than ever. If you grab a stake of ETH now, you'll be able to earn more ETH in the future with the stakes earned by just hodling your coins on your wallet.
On the other hand, NANO is a DAG-based cryptocurrency like IOTA and Constellation, with instant transactions, zero fees, and more. This means that the future lies on cryptocurrencies which could deliver unparalleled speeds, zero costs, and censorship resistance. DAG-based cryptocurrencies fit the bill quite nicely, and now it's the perfect time for you to buy them at cheap prices before it's too late. Just my thoughts