at some point megapixels become pointless, and more important is the light sensitivity (for concerts and nighttime, otherwise it'll be blurry and grainy as shit), and if the zoom is optical or digital... optical being the better.
Digital zoom works somewhat like in CSI, where they zoom in on a blurry black and white picture of the bad guy and go "computer, create pixels. enhance. contrast. Tint. Colour. and suddenly create a vivid full colour 3d image that can be rotated around so they notice the scar on the back of his neck that fits a vague description from a crazy hobo dude.