Quote from Jack_Larkin:
Oanda is great, but I'd highly suggest you stick with their fxTrade platform over MT4.
Their MT4 bridge setup is far from perfect, and most complaints I hear about the broker stem from trying to use MT4 instead of fxTrade.
You can always keep MT4 open for charting, writing custom indicators and such, but for execution and order management fxTrade is your best bet.
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FXCM... good company, good support... but they actually charge a higher spread markup for the use of MT4 over their native platform.
Unfortunately, their spreads are a little too wide to make scalping strategies effective. If you swing trade, low frequency stuff (a hand full or less trades a week) then you'll be fine... but if you like day trading then you'll have to look at their ActiveTrader platform instead of a standard account.
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TOS is a great platform but I haven't heard much out of them for forex... I use them for options trades and have been a client since before the TDA merger (and yes, things have gone down hill a bit since, sad really.)
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All that aside, are you from the US? Or do you live outside the US? I could point out a few more places to consider...