Best for Beginners: Acorns. Once your dollars land in your account, Acorns will automatically build a portfolio of stock and bond investments based on a brief questionnaire you complete when signing up for a new account. While active traders may be left wanting more, for the majority, Fidelity delivers, winning our award, No. These advanced tools include a performance risk tool which lets you figure out what will happen to your portfolio based on movement in an individual stock or options trade, or for your entire portfolio. Robinhood launched its mobile app before its website, making this a best stock trading app in its own right.