I bought a KSU Atwood pawpaw tree mail order. It started out as a twig 6 weeks ago. It produces bigger and darker green leaves than the native American pawpaw that was 3 times as big as the twig when I planted them both in-ground. Besides the leaf size, Atwood seems to grow at a faster rate than the American pawpaw. (But am not exactly sure if this is true.)
Are KSU pawpaw’s generally more vigorous and robust trees than the native American pawpaw?
The short answer I would say is no. You could easily have a more vigorous random seedling in a head to head battle.
There could be many reasons for vigor disparities between specimens.
You could plant 2 KSU Atwoods and have them grow at different rates.
But KSU Chappell is nearly universally accepted as a fast grower. And generally speaking a named variety would have a greater likelihood of having been selected partially for vigor versus a random seedling.
That KSU Atwood is grafted on to some rootstock, probably a random seedling. Seedling vigor varies widely and for most fruit trees can have a large impact on overall tree vigor.