This will depend if you are interested in getting your portfolio managed or if you will manage it on your own. If you don't have the time or the knoledge I would suggest to go for the VanguardGroup as returns are considered stable and the company is very well known for their portfolio managers. On the other hand, if you are looking to actively trade your account I recommend to choose between Fidelity and TD Ameritrade, both companies will deliver access to the financial markets in an efficient way. If you are a beginner trader, these two brokers will be especially important for your career as they provide excellent research and educational content that will help improve decision making.