There is no one camera that meets every customer's requirements. The entire image capture system must be considered: this includes camera, optics, and illumination. The specific application affects camera choice as well. Will it be a presentation mode scanner where the target can be moving in front of the camera? If so, motion blur is a major concern. Cameras with global shutter and progressive scan modes do significantly better at handling motion blur, but are more expensive. If target motion is not an issue, less expensive rolling shutter chips can be used.
The number of pixels in the camera needs to be enough to produce adequate sample density (1.6 pixels/module in linears, 2.0 pixels per module for 2Ds) on the largest bar codes you need to read. In addition, your lens choice needs to provide this sample density and stay in focus over a desirable working distance from the target bar code.
For high bar code read rates, the image produced by the camera system should be in focus, not be in saturation (white level at 255), not be too dark (whites < 30), and have decent seperation between the white and black levels (> 30). In addition, pixel noise in the image should be minimized.
Bob Dunphy