CurrencyFair and TransferWise both offer competitive exchange rates to the users which is significantly better than big banks. TransferWise offers real mid-market exchange rates while CurrencyFair offers 'peer-to-peer' exchange rates and many times help customers to beat existing exchange rates.
On the basis of ease of use, you can transfer money from a bank account, debit and credit card from TransferWise while CurrencyFair only accepts bank account transfers. You can use a debit card in CurrencyFair which are issued by the Irish government. On the basis of security, CurrencyFair and TransferWise both are secured by SSL security certificates to encrypt your login credentials and all other communications.