For practicing Tradovate is the best as they have no monthly chart fees. I do no know if they will extend my demo forever..so I might have to park 2k there to get sim charts for the life of my account.
ES
Here's a better idea. Get ahold of Advantage Futures or RJ O'Brien or Rosenthal Collins Group in Chicago or New York City.
Ask one of their account reps if you can go to their office and watch the 6E, ES, CL, ZN markets on an X-Trader DOM window between 9 am to 10 am Eastern US time.
It will save you a great deal of time and possibly money. It will answer all your questions.
Tradovate and sim charts and all of that retail gimmickry mean nothing compared to you physically sitting down 18 inches away from a screen with the real market in real time on a real connection on a real platform.