Some possibilities, based on my center and experience.
1) Driver A, runs all Air stops first, then goes back to the start of route and pretty much follows EDD. Driver B, Plans his morning and Air stops and derives a plan where he can get off a lot of ground while doing Air's. Starts in EDD where ever his last Air stop was and runs route from there. In this scenario, driver B will run route with less stops due to delivering grounds with air's at a bulk stop and not running the miles up.
2) Driver A, comes in at the start time, closes truck doors and heads out with a truck not loaded properly due to lack of training and understanding from the loader. Driver B, Comes in early and sets up truck and plans his day. In this case (all things being equal) Driver A will have a higher dispatch, but will probably run scratch or even over, while driver B will have a lower dispatch but run under.
3) Driver A, center knows that the driver can only handle X amount of stops to be under 9.5. Driver B, Center knows that they can add sections and stops as the driver works for free setting up truck, skips lunch and runs. In this case Driver B will have a bigger dispatch.
You mix all this together, and the guy who works for free, skips lunch, added stops on truck due to history of returning early, poor customer service, not filling out info notices, for a sig required. Rings bell and runs back to truck and speeds off in 3 seconds, cheats on pick up windows, runs, does not follow methods, prerecords stops in the AM, sits on seat belt to avoid telematics, deliver grounds to a business when making pick up at 4pm will have a higher dispatch and will run way under. did I miss anything?