I don't really know, in my riding school we did eventing and jumping. It is really great to start because you have to do a lot of flat work.
I always liked more jumping than eventing itself, even if I like cross-country.
I think that pure dressage is complicated for me to understand, because it depends on human judgment.
In showjumping, the pole is on the ground or not, the timer starts and stops, we are faster or slower...