Quote from nitro:
Professional Firms = Bright, Echo, etc, i.e., you put up your own money and payout is 100%
Proprietary Firms = Worldco, ETG, Shoenfeld, i.e., they put up the money, you get a percentage
Retail = Interactive Brokers, etc, e.g., SIPC protection, your own money, 100% payout.
Obviously, there are some that do 2 of the 3 above. AFAIK, there isn't a firm that can do all three.
nitro
Pointdirex provides all three.