Digital cameras: How much difference between 7.1mp and 6mp?

2 different type of cameras

In layman's terms your trying to compare a sedan to a suv.

These 2 models of cameras fall into 2 different classes. The Panasonic is a Superzoom camera where as the Canon A620 is all around point and shoot camera.

The Superzoom cameras have long zoom ranges and incorporate IS (Image Stabilization), these cameras are much larger than your typical P+S cameras. Most P+S cameras can fit in your pocket and are easy to take with you when out and about. Of course the P+S camera will not have the zoom range as the other camera, it comes down to what you want to use the camera for. Most casual photographers can make due with the shorter zoom range of a PS camera. If your plan is to use your camera for sporting events and other shooting situations then you want the longer zoom.

The Panasonic FZ7 matches up to Canon's S2IS if your want to compare 2 in the same class. The Canon A620 matches up to the Panasonic DMC-LX1. Of course there are plenty of other choices in either camera class, Sony, Nikon, Fuji, etc..

You yourself will know what your going to need the camera for, when your figure out which class of camera you want then look at equally matched cameras in both categories. Think about what your shooting, and if transporting a larger camera would restrict you from taking your camera with you.

FWIW both cameras are good at what they do.