~snip~
Among this two conditions, which is more dangerous than the other when on steering?
Both are dangerous but sleepiness on the steering is more dangerous to drunkeness because someone who is drunk can still get a good sense of belonging, just that the influence of the substance he took might be making him to drive in some kind of way but you see sleepiness on steering due to stress of not having enough sleep, it is more likely to cause an accident than someone who is under the influence of alcohol. I know someone that drinks so badly and most of the time he is always high on alcohol but he drives his car and haven't had any accident case all through his life, so it means he still have a sense of alertness whenever he is on the steering.
I initially thought that driving while intoxicated would be riskier, but after considering your points, I agreed that sleeping while driving is riskier. I have witnessed drunk drivers who knew where they were going and continued to drive regardless of the consequences, but there is no way to be asleep while driving, although both situations are risky and I don't pray anyone should get involved because they could result in an immediate accident and death.