I use two brokers. TradeStation is my main trading platform but I use E*Trade as a back up in case of disconnection during a day-trade. It also reduces my commission fees. TradeStation on a per share basis, so good for less than 1200 shares but E*Trade fixed commission of $9.99 per trade is cheaper when I trade more shares at once, i.e. above 1,200 shares per trade.