I like PascalCoin because it was designed to be efficient (more than 100 tx/sec on a core i7), its blockchain can be deleted, accounts cannot be created (they should be mined) and because accounts numbers are short, easy to memorize.
I think that it is undervalued because its exchange rate did not recover from the last crypto-currency "crash" (1 August 2017) without clear reason.
What exactly is nice about the ability to have blocks deleted?
From my understanding, the aim is to avoid to have an ininitely growing blockchain, keep a sufficient history of transaction history of all accounts. All the information is contained in the last X blocks. this leads to better performances on a long term (what is the cost of 100 tx per second per crypto-currency).
Accounts (like wallet addresses) cannot be created, they should be mined because only a defined number can exist to sustain such a system.
A few more details from the official website:
http://www.pascalcoin.org/Based on a groundbreaking and unique new idea in crypto, PascalCoin pioneers a new tier of scalability suitable for planetary-scale adoption. It is the first and only cryptocurrency to have broken the 100 transactions per second barrier!
By offering simple account numbers that can be associated to emails, company names and domain names, payments have never been easier.
PascalCoin’s powerful architecture lays the strong foundation for large-scale smart contracts in the form of Layer-2 protocols.
PascalCoin achieves all this by introducing a new cryptographic data-structure known as the SafeBox. The SafeBox compliments the Blockchain in a way that allows the Blockchain to be deleted whilst retaining its full cryptographic security.
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Infinite Scaling
Infinite Scaling is the ability for a cryptocurrency to run for an infinite period of time using the same amount of storage (at a constant throughput). All other cryptocurrencies will eventually fail over a long period of time since their history of transactions become so large that new nodes cannot synchronise and existing nodes run out of storage, among many other failures. PascalCoin is the first cryptocurrency to solve this major shortcoming.
Learn How PascalCoin achieves Infinite Scaling
Storing the Flow rather than the History of transactions
PascalCoin only keeps the last 100 blocks of the blockchain whilst retaining the cryptographic security of the full blockchain. It achieves this by using the SafeBox to keep track of user account balances and ownership whilst simultaneously retaining the aggregated proof-of-work difficulty within the SafeBox itself. In order to forge a SafeBox, it would require re-mining the entire history of blocks even though those blocks are no longer known (even by the network).
As a result, PascalCoin does not store the infinite history of transactions, only a short recent history of them. In this sense, PascalCoin stores the flow rather than the history of transactions, whilst retaining the full cryptographic SPV security of the history.