IOTA:

IOTA is a distributed ledger developed to handle transactions between connected devices in the IoT ecosystem, and its cryptocurrency is known as MIOTA.

IOTA uses a proprietary technology called the Tangle, which is a consensus algorithm that requires users to validate two transactions in order to complete their own IOTA transactions.

IOTA doesn't use blockchain at least, not in the same way as most other projects. IOTA had a vision of a different type of blockchain and set about to design its own system of validator nodes, called Tangle.

IOTA features feeless transactions, tamper-proof data, as well as low resource demand. Its network can power the Internet of Things (IoT) without heavy infrastructure investment requirements.

The nonsequential network of nodes that makes up Tangle is technically referred to as a Decentralized Acyclic Graph (DAG). As a direct consequence of this, a single node in a Tangle may serve as a connection to several other nodes.

Merits

1. Free transactions

2. Unlimited scaling

3. Can process any data, not just financial transactions

4. Hopes to achieve instant transactions

5. No IOTA mining - everyone contributes

6. Quantum resistant

Demerits

1) No finished product yet

2) Unclear when the project will be ready

3) Currently needing to use a centralized coordinator

4) Has experienced lots of technical flaws and bugs 5) Many (including MIT) think it has really bad security