Servo or stepper?

I have no experience with either servos or stepper motors and I’d like to find out which type is better suitable for my task. I need the motor to 1) be as small as possible, 2) rotate in an arc about 170 deg, than back to zero, on cue. It’s a lightweight task, there’s no load on the shaft. Accuracy is not essential, ±5 deg won’t make a difference. Should I use a servo or a stepper motor? I’ll be using it with the Uno. Any suggestions as to motor/shield etc. welcome. Thanks.

If you used a stepper you would need to add some way to sense the zero position so I'd use a hobby servo.

You also don't need a driver/controller to drive it, just a separate 5 or 6 volt power source (they tend to draw more power than the Arduino power supply can easily handle).