IOTA is an open-source distributed ledger (cryptocurrency) focused on providing secure communications and payments between machines on the Internet of Things. Using directed acyclic graph (DAG) technology instead of the traditional blockchain, IOTA's transactions are free regardless of the size of the transaction, confirmation times are fast, the number of transactions the system can handle simultaneously is unlimited, and the system can easily scale.
Ripple is a real-time gross settlement system (RTGS), currency exchange and remittance network by Ripple. Also called the Ripple Transaction Protocol (RTXP) or Ripple protocol,it is built upon a distributed open source Internet protocol, consensus ledger and native cryptocurrency called XRP (ripples).
I think both are good