I think just like in any race, it's all about speed, balance and control. in both road racing, drifting, autocross, rally racing, they practice the fine harmony between the basic three elements. Unlike road racing, where it depends on solid foundation of routine and mental discipline, drifing offers more of a freedom from that of the road racing. Where road racing will have ridgid rules and scoring systems, drifting will have style points judged by few individuals. I think that's where the seperation starts. In drifting, unlike road racing, whoever finishes first doesn't neccessarily finish as a winner, rather whoever gets more smoke, gets closer to the other car and drives crazier tend to win the competition, where stable and calculated drving along with actually finishing faster than anybody in the class will win you the race in road racing.
Like any auto-sports, the tires, suspension, cars layout, engine, will all be different.
I guess the concept of drifting being "show racing" comes from the lack of history behind the racing heritage of the sport itself, since it's fairely new compare to other established sports, and how the points system is very different from all of the other racing (rally, f-1, gt, road racing in general, auto-x, etc.). Difference being that it's not timed. You're not racing to get the fastest time.
I have some personal concerns about the judges who judge those events as well as how the score system works. Seems to me other similar sports that uses the same point system would be the figure skating, which doesn't really do too much for the sport's reputation. Just like ice skating, points are judged on the moves you make and there isn't a finish line where whoever gets there first wins (like speed skating). But both of the sports, both ice skating and drifting, takes considerable amount of skills and effort. But some people rather stay away from the "showiness" of the ice skating or drifting and rather prefer the traditional ice hockey or GT3 racing.