Hedge arbitrage or 2-legs arbitrage software specially created for find arbitrage situations between two brokers and trade in fully automated mode. You can use software for MT4 brokers and FIX API Brokers as well.
You can create hedging pair for arbitrage trading between MT4 and MT4, between MT4 and FIX API, and between FIX API and FIX API accounts.
Trading through FIX API allows you to be in full control of the outgoing data process (i.e., sending orders) and the incoming data process (i.e., receiving quotes) without any kind of intermediary
But most important benefit for FIX API Trading: you can use FOK or IOC orders and control slippage.
Fill or kill (FOK) is a type of time-in-force designation used in securities trading that instructs a brokerage to execute a transaction immediately and completely or not at all. This type of order is most likely to be used by active traders and is usually for a large quantity of stock.
IOC or Immediate Or Cancel is an attribute attached to a buy or sell order, to execute the transactions immediately or to cancel it.