UNUS SED LEO is an initiative started by Bitfinex that is focused on increasing the exchange's transparency. UNUS SED LEO means "one, but it's a lion" in Latin. The iniatative was created to increase the transparency of the exchange's finances, following a controversy related to the allocation of reserves from the stablecoin Tether, that was created by the same parent company as the Bitfinex exchange, iFinex. It is built around a token burning redemption mechanism which is tied to the parent company's revenues. Their dashboard provides insights into the fees that are collected, and the LEO tokens that are burned.

CEX.io is a British company that changed its focus from mining into becoming a cryptocurrency exchange. CEX has made an effort to add many coins, and boasts of fill-or-kill (FOK) orders that allow for some of the industry’s fastest trading, but it has a poor record on privacy and transparency that should give pause to traders.
The exchange’s fill-or-kill (FOK) orders are very fast, but come at a steep 7% fee. The mobile application is easy to use, and there is also an API integration. CEX is a regulated exchange that complies with all KYC and ALM laws, so they are able to accommodate several funding options, including credit cards and bank transfers.
The majority of CEX.io’s trading volume is done with bitcoin, and although they have made an effort to add more coins, this exchange simply does not have the trading options that others do. The low trading volume of other major coins provides limited liquidity for most traders.
Trading fees vary depending on trading volume between 0.16%-0.25%.Bank transfers are free and withdrawal fees are lower compared to their competitors, but transfers can take up to 20 days.
Although CEX.io is easy to use and allows for very fast crypto purchases, it has high fees, delayed withdrawal times, and a poor record on privacy/transparency.

Coinmama has become a reputable and reliable option for beginners looking to purchase bitcoin and ethereum. It has an easy to use interface, the option of instant purchasing via credit cards, and real time customer service. These reasons make it a very attractive option for people looking to get in to the world of cryptocurrencies easily.
Coinmama has a number of considerable disadvantages though. The very high fees, that can amount to 10%, on credit card purchases, are the main one. (There are no other funding options) They also don’t offer a wallet service, have no mobile application, or any additional trading tools.
Registering for an account on Coinmama is simple and straightforward. There is also a verification process, but it tends to be much shorter and less time consuming than other exchanges.
After users have opened an account and purchased bitcoin or ethereum, the funds are instantly transferred to a third-party wallet. This makes Coinmama very secure, as there is little chance of a breach.
Coinmama is able to process credit card payments because they require personal information and a government-issued ID. Furthermore, the privacy policy is very draconian; they reserve the right to obtain credit information about users before allowing them to purchase on the exchange and collect as much private information about users as they deem necessary before allowing them to purchase.
Despite this fact, it provides a basic on-ramp for users looking to buy bitcoin and ethereum for the first time.