Here's an ASCII of what I think the difference is in PWM width vs. requested counts:
Code:
883
|\ /
| \ /
| \ /
| \ /
| \ /
| |__|
884
|\ /
| \ /
| \ /
| \ /
| \ /
| \__/
Basically, I think both have a dead spot with the 884 having a smoother transition from the dead spot to an active state.