Jaylen's lateral agility, especially his eurosteps, are the thing that set him apart as an athlete. Few players in the NBA have that raw ability. Jackson has good agility, but not at Jaylen's elite level.
I think Jaylen is more explosive off of one feet that Jackson too. Although Jackson is a little more explosive off of two feet. Jaylen's wingspan is better than Jackson's, too.
Jaylen's form wasn't broken like Jackson's, who, unless he removes the hitch, will probably struggle with consistency. His free throw percentage is the best indication that he will struggle with shooting in the pros.
Jackson has good court vision, but it's not like Jaylen didn't have pretty good court vision in his own right (2 apg).
All in all, I don't think you can say "No doubt" that Jackson is a better prospect than Jaylen last year. I think I'd still rather have Jaylen.