Dorman Trading is a clearing member of the CME Group and clears hundreds of "local" Chicago floor traders.Mirus clears through Dorman Trading and Rosenthal Collins group. So what is the difference where to open an account,Mirus, Rosenthal or Dorman directly?
Customer service. Most of these clearers would prefer that the smaller retail account be handled by an ib, like Mirus, rather than internally. It is just not worth it for them to help you with your 10k account when they are dealing with clients who have far greater assets than you. You will get far better CS with Mirus if you have a problem than either Dorman or RCG.