The higher the optical zoom the better. Digital zoom does not move the image closer or farther optically. Instead, digital zoom takes the central part of the image required for the degree of zoom specified and throws away the rest. This will always result in a lower quality picture. Avoid cameras that only provide digital zoom.
Many cameras provide both optical and digital zoom.
On those cameras the optical zoom is the important factor. You can produce the same result as digital zoom with almost any image editing software. The result of capturing a digital image is a computer file. The size of the file depends on many factors. These factors include, image resolution, file format, and file compression.