Disneyland isn't Disneyland on Grad Night.... The atmosphere is replaced with the immature kids yelling over one another, and bad music. Cast Members aren't as nice because they don't want to put up with stupidity. A whole lot of things are closed, and you need to put up with a whole lot of superficial, self concerned, disrespectful, adolescents.
Disneyland, just isn't Disneyland on Grad Night. I'd rather put up with the larger crowds and mothers hitting me with prams during the day, with all the Disney additives, then what you get at a Grad Night.