Trying to determine point value based on which performance event is the most difficult vs. the easiest is an exercise destined to fail. Trying to compare different levels of performance is almost as difficult. For instance, the levels of agility only differ in the complexity of the course, the amount of time allowed, and the number of faults allowed. In Obedience, it's true that Open does build on Novice for the most part, but the only real similarity between Open and Utility is that the dogs do fronts and finishes. The jumps are different, the retrieves are different, and the emphasis on heeling has moved from major to cursory.
Tracking falls between.
Much is similar between a TD and a TDX as far as the basics of tracking go. It's just a methodology adopted to provide a base for the point spread used for all performance events. In theory, this allows for scores from a low of 165 to a high of 206. However, if the bell curve holds true, it's not likely that we would see many point totals below 170, or above 200. Agility does not lend itself well to using the same kind of methodology because there is such a small point variation in qualifying scores.