I back this up. Live photo affects the image quality when the light conditions are less than ideal, because it limits the shutter speed to minimum, when possible, which doesn't allow as much light to be captured by the sensor. You may notice that live photos are automatically turned off in night mode, and it's because the iPhone cannot keep the shutter speed low enough and just disables live photos in exchange for a longer exposure.

In ideal light conditions, the difference is negligible.