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1. In my personal opinion, Oanda is a great choice for traders who want to test the market with a really small amount of money. This is largely because of they allow flexilot contracts, which means they allow trades to be put on in any size: for instance, you can buy 43 Euros. This allows an extreme level of precision in risk management to be offered; traders can deposit any amount and still employ conservative risk management practices. With other brokers that only allow 1,000 unit lot sizes, this means that if you deposit $500, you have to use at least 2:1 leverage where each pip is likely to be around $.10 in value. If you wish to risk 2% on a trade in such a scenario, your stop must be 100 pips or less away. With flexilot sizing, you have more options and greater precision. For some trading styles this may not be very significant, but for those who view position sizing as their top priority, this may be an extremely important element.
2. Oanda also does not impose random fees -- namely inactivity or withdrawal fees -- and provides customers with interest earned on idle cash.
3. Oanda displays considerable transparency regarding its order book. This is most clearly displayed on its web site via the FX Labs tool, which features the company's order book of its customer accounts; the trading activity of its top traders; and the best trade placed each day, among other information.
4. In terms of technology, Oanda offers MT4 as well as its own custom platform, fxTrade (available via web and mobile). For MT4 users they offer an app store of sorts that allows traders incorporate add-ons made by other developers (some for free, others at a price) while fxTrade offers an API that lets traders connect their trading platform to other software they have that may scan the market and automatically place trade.
5. Spreads can fluctuate during market conditions, which is something that those trading very short timeframes, especially if they are doing so at fixed periods of time -- i.e. at the open or close of each session -- may wish to pay especially close attention to. In the interests of transparency, one of the values the company champions, live spreads are posted on the web site as well as a 7 day moving average of spreads.
6. Oanda provides support via phone, email, and live chat 24 hours a day, 5 days a week, in a variety of languages -- English, Russian, Italian, Chinese (Mandarin), German, Portuguese, Spanish, and French are the ones listed on the site.