Answer
Using the optical zoom is better.
Work Step by Step
Photographers prefer using an optical zoom because light from the desired subject falls upon all of the pixels in the sensor. This maximizes the resolution of the photograph, so that when an enlargement is printed, or one zooms in on the image on the computer screen, everything looks sharp.
When the digital zoom mode is used to take a picture, light from the desired subject falls upon a much smaller set of pixels in the middle of the sensor. (This is just like cropping the photo in-camera.) The photograph will have a lower resolution. If an enlargement is printed, each pixel is enlarged on the printed version, leading to the dreaded “pixelated” effect (search for “pixelated photo” to see examples).
