Different people need different amounts of sleep so "too little" sleep is relative. I had a sleep study done a month ago at the insistence of my wife due to snoring (no, I'm not fat, I breathe like Darth Vader when I sleep which I think is cool but my wife sadly does not). Anyhoo, the results I got back showed that of my time asleep, I am in the deep, restful sleep mode 92% of the time. So if I get 6 hours of sleep, most of that is restful. Others may only get 60-70% of restful sleep so they need 8 or 9 hours to get the same amount that I get.
So I guess what I'm trying to say is, I'm better than you.