I don't think there is any difference. Every story has to have a central conflict. However, both are still stories that will require a great deal of work in terms of structure, characterization, and so forth. About the only difference might be that the high-concept picture is less dependent upon the characters than the story, while the other story ceases to exist without those specific characters. For example, in a sitcom the characters are usually quickly identified by their widely varying speech patterns.
Dialogue is used to differentiate the characters.
No, no, because in this case the descriptions would be very similar. I mean, boys in a prep school tend to all look alike, unless you're going to go with a fat kid, a skinny kid, a bald kid, the jock, the nerd, those kind of contrasts. That was not what I wanted to do. Each character had to be described by what they were trying to accomplish, and the reason they were trying to accomplish it. That was something that had to evolve as the story evolved-I knew that this was not going to be one of those stories that hooks you by page five.