Pixels get all the attention but image details are what is really important to video surveillance users. The more image details, the more cases that can be solved and the fewer cameras that need to be deployed to obtain that evidence.
More pixels do not guarantee more image details. And megapixel does not ensure mega details.
This is obvious when cameras have either no light (e.g., night-time darkness) or too much light (e.g., looking at the sun). In those situations, it's hard to get any image, much less an extremely detailed one.
As I conduct megapixel camera tests, it is becoming increaseingly clear that pixel count cannot be accepted as is. It's better to think of the pixel count as the pixel potential or the maximum image detail that a megapixel camera can provide. However, some cameras and many common scenarios will provide significantly lower image detail than expected by the stated pixel count.
For instance, I am seeing that high resolutions and lower resolutions deliver the same visible image details. Conceptually, this should not happen -- a 2MP image should provide much greater image details than a 1.3MP or .5MP image - but it does.