IMO driving while tired is worse as the impairment creeps up on you for hours and you can stop at any time. There should be almost no impairment in your decision making.

On drugs it conceivable that you took a couple of shots and then your drunken mind decided to drive. In this case the decision to drive was made by someone impaired.

If you drive in a professional capacity your employer should be held accountable too. People that drive their employees to drive unsave should lose their business and spend some time in jail.