I like them due to their deep market liquidity and competitive spreads, they also have great stable conditions which are perfect for trading. I mostly used their automated trading and it requires backtesting on history. So I need high-quality data and it's available on the website. I find that their features are one of the most affordable among all of the other brokers that I have tried before. One of the reasons because all of their data are available in ticks and I can convert it into different timeframes, so there is no need to pay extra money for data from other vendors. If you need a good broker and high-quality data for testing your algorithms, I think Oanda can be a good go-to broker.