Open E cry - easy to master, easy to trade with, FREE to use FREE to sim (for 14 days). Commish is in line with the rest - remember, you can ALWAYS negotiate that fee. Also comes with free charts. Very stable.
Ninja Trader - new ver. 6 looks cool, free to play with and experiment. More features than Open E cry Dom but in order to use it for real trading you need to pay. Nevertheless, a good choice.
Try both and see which one floats your boat.