Most performance issues have little to do with precision and far more to do with how options behave as time passes and volatility environments change.
E*TRADE is one of the most popular investment platforms out there for a reason. Take a look at its current promotions and find out why they're worth checking out.
While Fidelity and E*TRADE are similar, one is better for active traders and the other is better for trading on the international market. Compare them here.