The higher the resolution, the more versatile the camera. Most of the consumer oriented higher resolution digital cameras will capture images at several different resolutions. This makes them very versatile. The best of these camera will also allow you to make good quality prints up to around 5x7. There are a few very inexpensive digital cameras on the market that use plastic lenses.
Most digital cameras use good quality optical glass.
The best of these, and most expensive, use aspherical glass lenses. Aspherical lenses are, as you might guess, not round. It seems that a perfectly round lens can produce a slight distortion to the image. Aspherical lenses can produce better pictures by reducing the distortion. Optical zoom is a very important feature on a digital camera.