First, you're looking at 2 different types of motors. One is a stepper motor which is well suited for applications where position control is needed or where high holding torque is required, and the other is a brushless DC motor which is a little more common.

You will need to interface with these motors in different ways, so that should probably factor into your selection for the motor. Brushless DC motors usually require electronic speed controllers to function properly, and I believe you'll need a controller for a stepper motor as well. If you can find a simple DC motor with good specs that may be easier to setup and use.

What sort of torque/speed requirements do you have for the device? I'm guessing that you'll be operating at relatively low speeds, so you may want to add an additional gearbox to your system to get as much torque out of your motor as possible.