Loopring is an Ethereum-based decentralized exchange protocol with an automated execution. Loopring is not a decentralized exchange. It is an infrastructure that enables decentralized exchange. Loopring is designed to allow any platform that uses smart contracts to integrate. By pooling all orders sent to its network, Loopring provides maximum liquidity and optimal pricing across exchanges and platforms. One of Loopring's unique features is that users don't need to deposit funds with an exchange. Tokens remain in wallets and are not locked by orders. In addition to not requiring direct deposits, the protocol has innovative mechanisms built in that allow for a series of trades to be bound together in an order ring to fulfill each other. The orders can then be split through order sharing, where partial orders will be filled until the whole amount is completely filled. This unique automated execution feature increases liquidity.
Loopring wants to become a cross-blockhain protocol. It has plans to integrate with NEO and Qtum.

BitFinex is a bitcoin to fiat exchange, a margin trading exchange, and a liquidity provider. The platform offers a number of features that expand the financial positions you can take - for example the ability to short Bitcoin via margin trading.
The exchange also offers a set of other cryptos apart from bitcoin such as Litecoin and Ethereum.
Deposits and withdrawals take place via the standard bank transfer means with fees of 0.1% and a minimum of $20. Bitcoin and Litecoin are free.
BitFinex takes security seriously and have moved from a hot wallet cold wallet set up to segregating customer funds where each user has access to their own wallet which they can review on the blockchain.
Bitfinex was hacked on 03 August 2016 and around 120,000 BTC were stolen.
Fee of 0.1% for most trades

Liquid is a blockchain platform that was created by the fintech company Quoine, that has a suite of blockchain powered financial services. Liquid is focused on providing liquidity to crypto industry. The platform offers a "worldbook" which is a multi-market order book that aggregates liquidity sources to one order book and supports trading in multiple currencies. Liquid has several features that are aimed at increasing the liquidity of crypto assets. The platform includes smart order routing, a currency conversion engine, fiat management, and other trading tools. Liquid is powered by the QASH token, which was released in an ICO that raised $105 million.