MB Trading has been plagued lately with quote delays whenever volume spikes. Needless to say this is a problem for day trading. They say they are fixing the problem. In the meantime, beware if trying to trade on market moving news.
I had an account with them a few years ago. It was used for swing and position trades only. Their quotes were constantly going down and orders were routinely getting stuck. Couldn't imagine ever using them to actively trade.
direct access firms let you trade directly with an ECN. they do not have to go through another brokerage before posting with an ECN.
tdameritrade trades against you (sells shares of your equity to you before getting the order to an ECN). therefore they are a brokerage not a direct access company. don't day trade or swing trade with a brokerage only direct access company's.