Motor graders are supposedly used in place of bulldozers when fine layering is required over a large area. Where bulldozers have in strength, they typically lack in finesse, which motor graders are for. They otherwise have the same ripper teeth and adjustable blade as bulldozers.
In practice, however, bulldozers prove to be far superior machines, capable of being far more effective at flattening than motor graders. Practical applications for motor graders seem to be few and far between, so prioritize getting bulldozers, wheel loaders, trucks, and other important vehicles with greater impact first.
The dozer blade on motor graders seems to be unable to depress low enough to get into the ground, resulting in it being unable to scrape the ground. In bumpier areas where the dozer blade can reach, the motor grader can get stuck with terrain propping it up in the middle and off its wheels.
Official Description: Motor graders are used on medium and large construction sites when large areas need to be flattened. They have a wide blade to spread soil and several lowerable ripper teeth at the rear to loosen layers of soil. Their articulated steering makes motor graders particularly manoeuvrable.