If you trade NYSE stocks, Assent is the one.
If you are a Nasdaq guy, it depends on the deal/training that you are getting wrt Assent & Hold.
Assent is a very professional organization, Hold Bros had the worst clearing system that I have ever seen in my life. Probably they must have changed it by now, otherwise they would not be in business.
I do not know Bright Trading, but from what I see Mr. Bright is a great guy, so have a look into their systems to before making up your mind.