My thought on the question as to "Are theravada practicioners more accomplished?" might to be first offer the idea that maybe accomplishments are not the focus of the practice, now should there be, to my mind, a competition between traditions over which tradition offers the "fast track" to enlightenment.
Having said that, one factor that is compelling to me is that Theravada has as its foundation the Tipitaka, and at the center of the foundation, the Vinaya and the Suttas. This foundation is what Buddha taught. If one is to follow the Buddha path, then it seems to me best, and most authentic, to study and practice what Buddha actually taught.
My comment above is not intended to detract from Zen or Vajrayana, but it seems an undisputed fact that these traditions are disconnected to a greater or lesser degree from the BuddhaDhamma. These traditions assume a platform of Dhamma, but they seem to me to be exotic or esoteric derivations of Dhamma, and not true Dhamma.
So, are Theravada practitioners more accomplished? Well, to my mind what the Buddha taught and instructed might be considered a roadmap for life and for release from dukkha. Theravada is a practice that follows the directions set forth on the roadmap. Other traditions might claim to be a tourist map to the same location, but these maps deviate from the course, send one over potholes in the road, create rest stops that are unnecessary, pass celebrity homes, direct one to sensual gardens, and some deviate so far as to lose their sense of direction completely.
If I'm on a journey and need to buy a map, I'll buy the one created by the original and authentic cartographer.