Groestlcoin is a blockchain payment protocol with a number of technical innovations and an active developer community. Groestlcoin was the first coin that activated SegWit and supports the Lightning Network. Transaction fees are very low and it claims to have instant payments. It is also one of the only coins that can be sent over SMS.
Groestlcoin's active developer community has made the payment protocol very adaptable, and it a popular coin among many crypto investors. Groestlcoin has an ASIC resistant Proof-of-Work consensus mechanism.

The Ampleforth token is a cryptocurrency with a variable supply. The total number of Ampleforth tokens in circulation changes daily and is adjusted according to the overall demand. The Ampleforth protocol is non-dilutive and ensures that the adjustments in supply that result in response to changes in demand occur proportionally across all the wallets in the network. This ensures that the percentage of each token holders overall ownership of the network remains stable, despite the adjustments in the overall token supply. The protocol is designed to reduce the correlation of the price of Ampleforth to the price of Bitcoin.

BitcoinDark is a fork of Bitcoin with a poorly defined purpose and use case. BitcoinDark is based on the InstantDEX protocol, a decentralized exchange for BitcoinDark and other cryptocurrencies supported by the project. The platform is also supposed to include a Pegged Asset Exchange (PAX) to allow users to buy and sell pegged assets – including fiat currencies, commodities, ETFs, and stocks.
BitcoinDark is a Proof-of-Stake (PoS) currency that has gained a significant market cap, but the project has failed to show how its vision will be implemented or how it will add value compared to other blockchain projects.